How Genes Are Controlled

How Genes Are Controlled
Chapter 11 How Genes Are Controlled

Biology and Society: Tobacco’s Smoking Gun
In 1996, researchers studying lung cancer found that, in human lung cells growing in the lab, a component of tobacco smoke, BPDE, binds to DNA within a gene called p53, which codes for a protein that normally helps suppress the formation of tumors. This work directly linked a chemical in tobacco smoke with the formation of human lung tumors. © 2013 Pearson Education, Inc. 2

HOW AND WHY GENES ARE REGULATED
In cellular differentiation, cells become specialized in structure and function. Certain genes are turned on and off in the process of gene regulation. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 3

Patterns of Gene Expression in Differentiated Cells
In gene expression, a gene is turned on and transcribed into RNA and information flows from genes to proteins and genotype to phenotype. Information flows from DNA to RNA to proteins. The great differences among cells in an organism must result from the selective expression of genes. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 4

Pancreas cell White blood cell Nerve cell Gene for a glycolysis enzyme
Figure 11.1 Colorized TEM Colorized SEM Colorized TEM Pancreas cell White blood cell Nerve cell Gene for a glycolysis enzyme Antibody gene Insulin gene Hemoglobin gene Figure 11.1 Patterns of gene expression in three types of human cells

Gene Regulation in Bacteria
Natural selection has favored bacteria that express only certain genes only at specific times when the products are needed by the cell. So how do bacteria selectively turn their genes on and off? © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 6

An operon includes a cluster of genes with related functions and the control sequences that turn the genes on or off. The bacterium E. coli uses the lac operon to coordinate the expression of genes that produce enzymes used to break down lactose in the bacterium’s environment. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 7

The lac operon uses a promoter, a control sequence where the transcription enzyme attaches and initiates transcription, an operator, a DNA segment that acts as a switch that is turned on or off, and a repressor, which binds to the operator and physically blocks the attachment of RNA polymerase and transcription. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 8

Operon turned off (lactose absent)
Figure 11.2 DNA mRNA Protein Operon turned off (lactose absent) DNA mRNA Protein Lactose Operon turned on (lactose inactivates repressor) Figure 11.2 The lac operon of E. coli

Genes for lactose enzymes
Figure 11.2a Operon Genes for lactose enzymes Promoter Regulatory gene Operator DNA 1 2 mRNA RNA polymerase cannot attach to promoter Active repressor Protein Operon turned off (lactose absent) Figure 11.2 The lac operon of E. coli (part 1)

Operon turned on (lactose inactivates repressor)
Figure 11.2b 4 Transcription DNA RNA polymerase bound to promoter 3 mRNA 5 Translation 2 Protein 1 Inactive repressor Lactose enzymes Lactose Operon turned on (lactose inactivates repressor) Figure 11.2 The lac operon of E. coli (part 2)

Gene Regulation in Eukaryotic Cells
Eukaryotic cells have more complex gene regulating mechanisms with many points where the process can be turned on or off. The multiple mechanisms that control gene expression are like the many control valves along a water supply. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 12

Figure 11.3 The gene expression “pipeline” in a eukaryotic cell
Chromosome Unpacking of DNA DNA Gene Transcription of gene Intron Exon RNA transcript Processing of RNA Flow of mRNA through nuclear envelope Nucleus Cap Tail mRNA in nucleus Cytoplasm mRNA in cytoplasm Breakdown of mRNA Translation of mRNA Polypeptide Various changes to polypeptide Breakdown of protein Active protein Figure 11.3 The gene expression “pipeline” in a eukaryotic cell

Chromosome Unpacking of DNA DNA Gene Transcription of gene Intron Exon
Figure 11.3a Chromosome Unpacking of DNA DNA Gene Transcription of gene Intron Exon RNA transcript Figure 11.3 The gene expression “pipeline” in a eukaryotic cell (part 1)

Flow of mRNA through nuclear envelope
Figure 11.3b Processing of RNA Flow of mRNA through nuclear envelope Nucleus Cap Tail mRNA in nucleus Cytoplasm mRNA in cytoplasm Breakdown of mRNA Figure 11.3 The gene expression “pipeline” in a eukaryotic cell (part 2)

The Regulation of DNA Packing
Cells may use DNA packing for long-term inactivation of genes. X chromosome inactivation takes place early in embryonic development, occurs in female mammals, and is when one of the two X chromosomes in each cell is inactivated at random. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 16

The Regulation of DNA Packing
All of the descendants of each cell will have the same X chromosome turned off. If a female is heterozygous for a gene on the X chromosome, about half her cells will express one allele and the others will express the alternate allele. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 17

Cell division and X chromosome
Figure 11.4 Two cell populations in adult cat: Early embryo: X chromosomes Active X Cell division and X chromosome inactivation Orange fur Inactive X Allele for orange fur Inactive X Allele for black fur Black fur Active X Figure 11.4 X chromosome inactivation: the tortoiseshell pattern on a cat

X chromosomes Cell division and X chromosome inactivation
Figure 11.4a Two cell populations in adult cat: Early embryo: Active X X chromosomes Cell division and X chromosome inactivation Orange fur Inactive X Allele for orange fur Inactive X Allele for black fur Black fur Active X Figure 11.4 X chromosome inactivation: the tortoiseshell pattern on a cat (detail)

The Initiation of Transcription
The initiation of transcription is the most important stage for regulating gene expression. In prokaryotes and eukaryotes, regulatory proteins bind to DNA and turn the transcription of genes on and off. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 20

Animation: Initiation of Transcription
The Initiation of Transcription Transcription in eukaryotes, unlike in prokaryotes, is complex, involving many proteins, called transcription factors, that bind to DNA sequences called enhancers. Animation: Initiation of Transcription © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 21

Enhancers (DNA control sequences)
Figure 11.5 Enhancers (DNA control sequences) RNA polymerase Bend in the DNA Transcription Gene Transcription factor Promoter Figure 11.5 A model for turning on a eukaryotic gene

The Initiation of Transcription
Repressor proteins called silencers bind to DNA and inhibit the start of transcription. Activators are more typically used by eukaryotes than silencers and turn genes on by binding to DNA. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 23

RNA Processing and Breakdown
The eukaryotic cell localizes transcription in the nucleus and processes RNA in the nucleus. RNA processing includes the addition of a cap and tail to the RNA, removal of any introns, and splicing together of the remaining exons. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 24

In alternative RNA splicing, exons may be spliced together in different combinations, producing more than one type of polypeptide from a single gene. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 25

A typical human gene contains about ten exons, with nearly all human genes spliced in at least two different ways and some spliced hundreds of different ways! Animation: RNA Processing Animation: Blocking Translation Animation: mRNA Degradation © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 26

1 2 3 4 5 Exons DNA Introns Figure 11.6-1
Figure 11.6 Alternative RNA splicing: producing multiple mRNAs from the same gene (step 1)

1 2 3 4 5 1 2 3 4 5 Exons DNA Introns RNA transcript Figure 11.6-2
Figure 11.6 Alternative RNA splicing: producing multiple mRNAs from the same gene (step 2)

1 2 3 4 5 1 2 3 4 5 1 2 3 5 1 2 4 5 Exons DNA Introns RNA transcript
Figure Exons DNA 1 2 3 4 5 Introns RNA transcript 1 2 3 4 5 RNA splicing or mRNA 1 2 3 5 1 2 4 5 Figure 11.6 Alternative RNA splicing: producing multiple mRNAs from the same gene (step 3)

Eukaryotic mRNAs can last for hours to weeks to months and are all eventually broken down and their parts recycled. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 30

microRNAs Small single-stranded RNA molecules, called microRNAs (miRNAs), bind to complementary sequences on mRNA molecules in the cytoplasm. Some trigger the breakdown of their target mRNA, and others block translation. It has been estimated that miRNAs may regulate the expression of up to one-third of all human genes, yet miRNAs were unknown 20 years ago! © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 31

The Initiation of Translation
The process of translation offers additional opportunities for regulation by regulatory molecules. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 32

Protein Activation and Breakdown
Post-translational control mechanisms in eukaryotes occur after translation and often involve cutting polypeptides into smaller, active final products. Animation: Protein Processing Animation: Protein Degradation © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 33

Initial polypeptide (inactive)
Figure Initial polypeptide (inactive) Figure 11.7 The formation of an active insulin molecule (step 1)

Initial polypeptide (inactive) Insulin (active hormone)
Figure Cutting Initial polypeptide (inactive) Insulin (active hormone) Figure 11.7 The formation of an active insulin molecule (step 2)

Cell Signaling In a multicellular organism, gene regulation can cross cell boundaries. A cell can produce and secrete chemicals, such as hormones, that affect gene regulation in another cell. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 36

Transcription factor (activated)
Figure 11.8 SIGNALING CELL 1 Secretion Signal molecule Plasma membrane 2 3 4 TARGET CELL Receptor protein Transcription factor (activated) Nucleus 5 Response Transcription New protein mRNA 6 Translation Figure 11.8 A cell-signaling pathway that turns on a gene

Transcription factor (activated)
Figure 11.8a SIGNALING CELL 1 Secretion Signal molecule Plasma membrane 2 3 4 TARGET CELL Receptor protein Transcription factor (activated) Figure 11.8 A cell-signaling pathway that turns on a gene (part 1)

5 6 Nucleus Response Transcription New protein mRNA Translation
Figure 11.8b Nucleus 5 Response Transcription New protein mRNA 6 Translation Figure 11.8 A cell-signaling pathway that turns on a gene (part 2)

Homeotic genes Master control genes called homeotic genes regulate groups of other genes that determine what body parts will develop in which locations. Mutations in homeotic genes can produce bizarre effects. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 40

Mutant fly with extra legs growing from head Normal head
Figure 11.9 Antenna Eye Extra pair of legs Mutant fly with extra legs growing from head Normal head Figure 11.9 The effect of homeotic genes

Antenna Eye Normal head Figure 11.9a
Figure 11.9 The effect of homeotic genes (part 1)

Mutant fly with extra legs growing from head
Figure 11.9b Extra pair of legs Mutant fly with extra legs growing from head Figure 11.9 The effect of homeotic genes (part 2)

Fruit fly embryo (10 hours) Mouse embryo (12 days)
Figure 11.10 Fruit fly chromosome Mouse chromosomes Fruit fly embryo (10 hours) Mouse embryo (12 days) Adult fruit fly Adult mouse Figure Homeotic genes in two different animals

DNA Microarrays: Visualizing Gene Expression
A DNA microarray allows visualization of gene expression. The pattern of glowing spots enables the researcher to determine which genes were being transcribed in the starting cells. Researchers can thus learn which genes are active in different tissues or in tissues from individuals in different states of health. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. The broad concept of selective “reading” of the genetic code associated with differentiation and types of cellular activity can be missed when concentrating on the extensive details of regulation. Analogies, noted below in the teaching tips, can help students relate this overall selective process to their own experiences. Students already understand the selective reading of relevant chapters in textbooks and the selective referencing of product manuals to get answers to different questions. These experiences are similar in many ways to the broad processes of gene regulation. 2. The many levels of gene regulation in eukaryotic cells can be confusing and frustrating. The water pipe analogy depicted in Figure 11.3 can be a helpful reference to organize the potential sites of regulation. Teaching Tips 1. Cellular differentiation is analogous to buying a book about how to build birdhouses and reading only the plans needed to build one particular model. Although the book contains directions to build many different birdhouses, you read and follow only the directions for the particular birdhouse you choose to build. The pages and directions for the other birdhouses remain intact. When cells differentiate, they read, or express, only the genes that are needed in that particular cell type. 2. The lactose operon is turned on by removing the repressor—a sort of double negative. Students might enjoy various analogies to other types of “double negatives,” such as “When the cat’s away, the mice will play.” In another analogy, if Mom keeps the kids away from the cookies, but somebody occupies her attention, kids can sneak by and snatch some cookies. In this last analogy, the person occupying Mom’s attention functions most like lactose binding to the repressor. 3. A key advantage of an operon system is the ability to turn off or on a set of genes with a single “switch.” You can demonstrate this relationship in your classroom by turning off or on a set of lights with a single switch. 4. The authors develop an analogy between the regulation of transcription and the series of water pipes that carry water from your local water supply, perhaps a reservoir, to a faucet in your home. At various points, valves control the flow of water. Similarly, the expression of genes is controlled at many points along the process. Figure 11.3 illustrates the “flow” of genetic information from a chromosome—a reservoir of genetic information—to an active protein that has been made in the cell’s cytoplasm. The multiple mechanisms that control gene expression are analogous to the control valves in water pipes. In the figure, a possible control knob indicates each gene expression “valve.” In the figure, the large size of the transcription control knob highlights its crucial role. 5. Just as a folded map is difficult to read, DNA packaging tends to prevent gene “reading” or expression. 6. Just as boxes of your things that will be little used are packed deeper into a closet, attic, or basement, chromatin that is not expressed is highly compacted and is stored away. 7. Alternative RNA splicing is like remixing music to produce a new song or re-editing a movie for a different ending. You could have a little fun by challenging students to identify which category of academic award is most like alternative RNA splicing. (Answer: the award for best editing.) 8. The action of an extracellular signal reaching a cell’s surface is like pushing the doorbell at a home. The signal is converted to another form (pushing a button rings a bell) and activities change within the house as someone comes to answer the door. 9. Students might wonder why a patch of color is all the same on the cat’s skin in Figure 11.4, if every cell has an equal chance of being one of the two color forms. The answer is that X chromosome inactivation occurs early in development. Thus, the patch of one color represents the progeny of one embryonic cell after X chromosome inactivation. 10.Homeotic genes are often called “master control genes.” The relationship between homeotic genes and structural genes is like the relationship between a construction supervisor and the workers. Major rearrangements can result from a few simple changes in the directions for construction. 11. There is much hope in the use of DNA microarrays to refine cancer therapies. In the past, a diagnosis of cancer was too often met with general treatments that benefited only a fraction of the patients. Physicians were left to wonder why some people with breast cancer or lung cancer responded to therapy while others did not. DNA microarrays enable us to identify differences between patients with the same apparent type of cancer (breast, lung, prostate, and so on). Consider sharing this important avenue of hope. It is likely that some of your students will soon have a family member facing these battles. 45

Figure 11.11 1 mRNA isolated Reverse transcriptase combined with fluorescently labeled DNA nucleotides 2 cDNA made from mRNA Fluorescent cDNA DNA microarray (each well contains DNA from a particular gene) 3 cDNA mixture added to wells 4 Unbound cDNA rinsed away Nonfluorescent spot Fluorescent spot Fluorescent cDNA DNA microarray (6,400 genes) DNA of an expressed gene DNA of an unexpressed gene Figure Visualizing gene expression using a DNA microarray

Figure 11.11a 1 mRNA isolated Reverse transcriptase combined with fluorescently labeled DNA nucleotides 2 cDNA made from mRNA Fluorescent cDNA Figure Visualizing gene expression using a DNA microarray (part 1)

DNA microarray (each well contains DNA from a particular gene)
Figure 11.11b DNA microarray (each well contains DNA from a particular gene) 3 cDNA mixture added to wells 4 Unbound cDNA rinsed away Nonfluorescent spot Fluorescent spot Figure Visualizing gene expression using a DNA microarray (part 2)

DNA microarray (6,400 genes)
Figure 11.11c Nonfluorescent spot Fluorescent spot Fluorescent cDNA DNA microarray (6,400 genes) DNA of an expressed gene DNA of an unexpressed gene Figure Visualizing gene expression using a DNA microarray (part 3)

CLONING PLANTS AND ANIMALS The Genetic Potential of Cells
Differentiated cells all contain a complete genome and have the potential to express all of an organism’s genes. Differentiated plant cells can develop into a whole new organism. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 50

Cells removed from orchid plant Cells in growth medium Cell division
Figure Single cell Cells removed from orchid plant Cells in growth medium Cell division in culture Young plant Adult plant Figure Test-tube cloning of an orchid (step 5)

The Genetic Potential of Cells
The somatic cells of a single plant can be used to produce hundreds or thousands of identical organisms—clones from a single plant. Plant cloning demonstrates that cell differentiation in plants is reversible and does not cause irreversible changes in the DNA. Plant cloning is now used extensively in agriculture. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 52

Regeneration is the regrowth of lost body parts and occurs, for example, in the regrowth of the legs of salamanders. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 53

During regeneration of the leg, cells in the leg stump reverse their differentiated state, divide, and then differentiate again to give rise to a new leg. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 54

Reproductive Cloning of Animals
Nuclear transplantation involves replacing the nucleus of an egg cell with the nucleus from a differentiated cell from an adult body and allowing the egg to develop into an adult. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 55

Reproductive Cloning of Animals
In 1997, Scottish researchers produced Dolly, a sheep, by replacing the nucleus of an egg cell with the nucleus of an adult somatic cell. This procedure is called reproductive cloning, because it results in the birth of a new animal. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 56

Nucleus from donor cell
Figure 11.13 Reproductive cloning Donor cell Nucleus from donor cell Implant embryo in surrogate mother Clone of donor is born Therapeutic cloning Remove nucleus from egg cell Add somatic cell from adult donor Grow in culture to produce a blastocyst (early embryo) Remove embryonic stem cells from embryo and grow in culture Induce stem cells to form specialized cells for therapeutic use Figure Cloning by nuclear transplantation

Implant embryo in surrogate mother Clone of donor is born
Figure 11.13b Reproductive cloning Implant embryo in surrogate mother Clone of donor is born Therapeutic cloning Remove embryonic stem cells from embryo and grow in culture Induce stem cells to form specialized cells for therapeutic use Figure Cloning by nuclear transplantation (part 2)

Figure 11.13c Figure Cloning by nuclear transplantation (photo)

Practical Applications of Reproductive Cloning
Since Dolly, reproductive cloning has been used to clone many species of mammals, including mice, horses, dogs, mules, cows, pigs, rabbits, ferrets, and cats. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 60

Reproductive cloning has been used to restock populations of endangered species including a wild mouflon (a small European sheep), a banteng (a Javanese cow), a gaur (an Asian ox), and gray wolves. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 61

However, cloning does not increase genetic diversity, which may be essential to long-term species survival. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 62

(a) The first cloned cat (b) Cloning for medical use
Figure 11.14 (a) The first cloned cat (b) Cloning for medical use (c) Clones of endangered animals Mouflon lamb with mother Banteng Gaur Gray wolf Figure Reproductive cloning of mammals

(c) Clones of endangered animals
Figure 11.14c (c) Clones of endangered animals Mouflon lamb with mother Banteng Gaur Gray wolf Figure Reproductive cloning of mammals (endangered animals)

Critics raise practical and ethical objections to human cloning.
Cloning of mammals has heightened speculation about human cloning and is very difficult and inefficient. Critics raise practical and ethical objections to human cloning. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 65

Embryonic stem cells (ES cells)
are derived from blastocysts and can give rise to all the specialized cells in the body. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 66

Adult Stem Cells Adult stem cells are cells in adult tissues and
generate replacements for some of the body’s cells. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 67

Blast Animation: Stem Cells
Adult Stem Cells Unlike embryonic ES cells, adult stem cells are partway along the road to differentiation and usually give rise to only a few related types of specialized cells. Blast Animation: Stem Cells © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 68

Adult stem cells in bone marrow Blood cells Nerve cells Cultured
Figure 11.15 Adult stem cells in bone marrow Blood cells Nerve cells Cultured embryonic stem cells Heart muscle cells Different culture conditions Different types of differentiated cells Figure Differentiation of embryonic stem cells in culture

Umbilical Cord Blood Banking
can be collected at birth, contains partially differentiated stem cells, and has had limited success in the treatment of a few diseases. The American Academy of Pediatrics recommends cord blood banking only for babies born into families with a known genetic risk. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often fail to see the similarities between identical twins and cloning. Each process produces multiple individuals with identical nuclear genetic material. 2. Students often assume that clones will appear and act identically. This misunderstanding provides an opportunity to discuss the important influence of the environment in shaping the final phenotype. 3. Students might not immediately understand why reproductive cloning is necessary to transmit specific traits in farm animals. They may fail to realize that unlike cloning, sexual reproduction mixes the genetic material and may not produce offspring with the desired trait(s). Teaching Tips 1. The researchers who cloned Dolly the sheep from a mammary gland cell named Dolly after the celebrity Dolly Parton. 2. An even more remarkable aspect of salamander limb regeneration is that only the missing limb segments are regenerated. If an arm is amputated at the elbow, only the forearm, wrist, and hand are regenerated. Somehow, the cells can detect what is missing and replace only those parts! 3. Preimplantation genetic diagnosis (PGD) is a genetic screening technique that removes one or two cells from an embryo at about the 6- to 10-cell stage. The cells that are removed are genetically analyzed, whereas the remaining embryonic cell mass retains the potential to develop into a normal individual. This technique permits embryos to be genetically screened before implanting them into a woman. However, PGD has another potential use. Researchers can use PGD to obtain embryonic stem cells without destroying a human embryo. This procedure might be more acceptable than methods that destroy the embryo to obtain embryonic stem cells. 4. The transplantation of pig or other nonhuman tissues into humans (called xenotransplantation) risks the introduction of pig (or other animal) viruses into humans. This viral DNA might not otherwise have the capacity for transmission to humans. 5. Political restrictions on the use of federal funds to study stem cells from various sources illustrate the influence of society on the directions of science. As time permits, consider opportunities to discuss or investigate this and other ways that science and society interact. 70

Figure 11.16 Figure Umbilical cord blood banking

THE GENETIC BASIS OF CANCER
Cancer is a variety of diseases in which cells experience changes in gene expression and escape from the control mechanisms that normally limit their growth and division. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 72

Genes That Cause Cancer
As early as 1911, certain viruses were known to cause cancer. Oncogenes are genes that cause cancer and found in viruses. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 73

Oncogenes and Tumor-Suppressor Genes
Proto-oncogenes are normal genes with the potential to become oncogenes, found in many animals, and often genes that code for growth factors, proteins that stimulate cell division. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 74

A cell can acquire an oncogene from a virus or from the mutation of one of its own proto-oncogenes. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 75

Gene in new position, under new controls Normal growth-stimulating
Figure 11.17 Proto-oncogene DNA Mutation within gene Multiple copies of gene Gene in new position, under new controls New promoter Oncogene Hyperactive growth-stimulating protein Normal growth-stimulating protein in excess Figure How a proto-oncogene can become an oncogene

inhibit cell division, prevent uncontrolled cell growth, and may be mutated and contribute to cancer. Researchers have identified many mutations in both tumor-suppressor and growth factor genes that are associated with cancer. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 77

(b) Uncontrolled cell growth (cancer)
Figure 11.18 Tumor-suppressor gene Mutated tumor-suppressor gene Defective, nonfunctioning protein Normal growth- inhibiting protein Cell division under control Cell division not under control (a) Normal cell growth (b) Uncontrolled cell growth (cancer) Figure Tumor-suppressor genes

Figure 11.19 Tumor Figure A magnetic resonance image (MRI) machine can be used to visualize a brain tumor.

The Progression of a Cancer
Nearly 150,000 Americans will be stricken by cancer of the colon (the main part of the large intestine) this year. Colon cancer, like many cancers, spreads gradually and is produced by more than one mutation. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 80

Cellular changes: Increased cell division
Figure 11.20 Cellular changes: Increased cell division Cellular changes: Growth of benign tumor Cellular changes: Growth of malignant tumor Colon wall Colon wall DNA changes: Oncogene activated DNA changes: Tumor-suppressor gene inactivated DNA changes: Second tumor-suppressor gene inactivated Figure Stepwise development of a typical colon cancer

The Progression of a Cancer
The development of a malignant tumor is accompanied by a gradual accumulation of mutations that convert proto-oncogenes to oncogenes and knock out tumor-suppressor genes. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 82

1 mutation 2 mutations 3 mutations 4 mutations Malignant cell
Figure Chromosomes 1 mutation 2 mutations 3 mutations 4 mutations Normal cell Malignant cell Figure Accumulation of mutations in the development of a cancer cell (step 5)

In familial or inherited cancer,
Most mutations that lead to cancer arise in the organ where the cancer starts. In familial or inherited cancer, a cancer-causing mutation occurs in a cell that gives rise to gametes and the mutation is passed on from generation to generation. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 84

“Inherited” Cancer Breast cancer
is usually not associated with inherited mutations and in some families can be caused by inherited BRCA1 cancer genes. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 85

Figure 11.22 Figure Breast cancer

Cancer Risk and Prevention
is the second leading cause of death (after heart disease) in most industrialized countries and can be caused by carcinogens, cancer-causing agents, found in the environment, including tobacco products, alcohol, and exposure to ultraviolet light from the sun. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 87

Table 11.1 Table 11.1 Cancer in the United States

Cancer Risk and Prevention
Exposure to carcinogens is often an individual choice and can be avoided. Some studies suggest that certain substances in fruits and vegetables may help protect against a variety of cancers. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 89

Evolution Connection: The Evolution of Cancer in the Body
Evolution drives the growth of a tumor. Like individuals in a population of organisms, cancer cells in the body have the potential to produce more offspring than can be supported by the environment and show individual variation, which affects survival and reproduction and can be passed on to the next generation of cells. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 90

Evolution Connection: The Evolution of Cancer in the Body
Some researchers are attempting to “prime” tumors for treatment by increasing the reproductive success of only those cells that will be susceptible to a chemotherapy drug. © 2013 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students typically have little background knowledge of cancer at the cellular level. Consider creating your own pretest to inquire about your students’ entering knowledge of cancer. For example, ask students if all cancers are genetic (yes, all cancers are based on genetic errors and are the main subject of this chapter). In addition, ask students if exposure to a virus can lead to cancer (yes, as noted in the text). 2. Students often conclude falsely that most breast cancer is associated with known mutations in the breast cancer genes BRCA1 and BRCA2. However, the vast majority of breast cancer has no known inherited association. 3. Many students do not appreciate the increased risk of skin cancer and premature aging associated with the use of tanning beds. Teaching Tips 1. Tumor-suppressor genes function like the repressor in the E. coli lactose operon. The lac operon is expressed and cancers appear when their respective repressors do not function. 2. The production of a vaccine (Gardasil) against a virus known to contribute to cervical cancer has helped students become aware of the risks of HPV exposure. The following website of the National Cancer Institute describes the risks of HPV infection ( 3. Students who have had a leg, hip, or back X-rayed may recall a lead apron placed over their abdominal and pelvic region. The lead apron is to prevent the irradiation of the patient’s gonads, which could cause mutations that would be inherited. 4. Students may not realize the possible consequences of testing positive for a predisposition to cancer. Although illegal, health insurance companies could use that information to deny insurance to people who are more likely to get ill. (The Genetic Information Nondiscrimination Act of 2008 prohibits discrimination in health coverage and employment based upon genetic information.) Furthermore, people may feel obliged or be obligated to share this information with a potential mate or employer. 5. Exposure to carcinogens early in life generally carries greater risks than the same exposure later in life. This is because damage in early life has more time to accumulate additional mutations potentially leading to disease. 6. Nearly one in five deaths in the United States results from the use of tobacco. Additional information on the risks of tobacco can be found at the website of the American Cancer Society ( 91

Figure 11.UN01 Figure 11.UN01 In-text figure, DNA packing icon, p. 202

Figure 11.UN02 Figure 11.UN02 In-text figure, transcription initiation icon, p. 203

Figure 11.UN03 Figure 11.UN03 In-text figure, RNA processing icon, p. 204

Figure 11.UN04 Figure 11.UN04 In-text figure, translation initiation Icon, p. 204

A typical operon Regulatory gene Promoter Operator Gene 1 Gene 2
Figure 11.UN05 A typical operon Regulatory gene Promoter Operator Gene 1 Gene 2 Gene 3 DNA Produces repressor that in active form attaches to operator RNA polymerase binding site Switches operon on or off Code for proteins Figure 11.UN05 Summary of Key Concepts: Gene Regulation in Bacteria

DNA unpacking Transcription RNA processing RNA transport
Figure 11.UN06 DNA unpacking Transcription RNA processing RNA transport mRNA breakdown Translation Protein activation Protein breakdown Figure 11.UN06 Summary of Key Concepts: Pipeline Icon

Embryo implanted in surrogate mother Clone of nucleus donor
Figure 11.UN07 Nucleus from donor cell Early embryo resulting from nuclear transplantation Embryo implanted in surrogate mother Clone of nucleus donor Figure 11.UN07 Summary of Key Concepts: Reproductive Cloning of Animals

Nucleus from donor cell Early embryo resulting from nuclear
Figure 11.UN08 Nucleus from donor cell Early embryo resulting from nuclear transplantation Embryonic stem cells in culture Specialized cells Figure 11.UN08 Summary of Key Concepts: Therapeutic Cloning and Stem Cells

Proto-oncogene (normal) Oncogene Mutation Normal protein Mutant
Figure 11.UN09 Proto-oncogene (normal) Oncogene Mutation Normal protein Mutant protein Normal regulation of cell cycle Out-of-control growth (leading to cancer) Normal growth-inhibiting protein Defective protein Mutation Tumor-suppressor gene (normal) Mutated tumor-suppressor gene Figure 11.UN09 Summary of Key Concepts: Genes That Cause Cancer

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