1. © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey Chapter 11 How Genes Are Controlled

2.  Cloning is the creation of an individual by asexual reproduction.  The ability to clone an animal from a single cell demonstrates that every adult body cell –contains a complete genome that is –capable of directing the production of all the cell types in an organism. Introduction © 2012 Pearson Education, Inc.

3.  Cloning has been attempted to save endangered species.  However, cloning –does not increase genetic diversity and –may trivialize the tragedy of extinction and detract from efforts to preserve natural habitats. Introduction © 2012 Pearson Education, Inc.

4. Figure 11.0_1 Chapter 11: Big Ideas Control of Gene Expression Cloning of Plants and Animals The Genetic Basis of Cancer

5. CONTROL OF GENE EXPRESSION © 2012 Pearson Education, Inc.

6.  Gene regulation is the turning on and off of genes.  Gene expression is the overall process of information flow from genes to proteins.  The control of gene expression allows cells to produce specific kinds of proteins when and where they are needed.  Our earlier understanding of gene control came from the study of E. coli. 11.1 Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes © 2012 Pearson Education, Inc.

7. Figure 11.1A E. coli

8. 11.1 Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes  A cluster of genes with related functions, along with the control sequences, is called an operon.  With few exceptions, operons only exist in prokaryotes. © 2012 Pearson Education, Inc.

9. 11.1 Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes  When an E. coli encounters lactose, all the enzymes needed for its metabolism are made at once using the lactose operon.  The lactose (lac) operon includes 1.three adjacent lactose-utilization genes, 2.a promoter sequence where RNA polymerase binds and initiates transcription of all three lactose genes, and 3.an operator sequence where a repressor can bind and block RNA polymerase action. © 2012 Pearson Education, Inc.

10. 11.1 Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes  Regulation of the lac operon –A regulatory gene, located outside the operon, codes for a repressor protein. –In the absence of lactose, the repressor binds to the operator and prevents RNA polymerase action. –Lactose inactivates the repressor, so –the operator is unblocked, –RNA polymerase can bind to the promoter, and –all three genes of the operon are transcribed. © 2012 Pearson Education, Inc.

11. Figure 11.1B Operon turned off (lactose is absent): OPERON Regulatory gene Promoter Operator Lactose-utilization genes RNA polymerase cannot attach to the promoter Active repressor Protein mRNA DNA Protein mRNA DNA Operon turned on (lactose inactivates the repressor): RNA polymerase is bound to the promoter Lactose Inactive repressor Translation Enzymes for lactose utilization

12. 11.1 Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes  There are two types of repressor-controlled operons. –In the lac operon, the repressor is –active when alone and –inactive when bound to lactose. –In the trp bacterial operon, the repressor is –inactive when alone and –active when bound to the amino acid tryptophan (Trp). © 2012 Pearson Education, Inc.

13. Figure 11.1C Inactive repressor Active repressor Lactose Tryptophan DNA Promoter Operator Gene lac operon trp operon

14. 11.1 Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes  Another type of operon control involves activators, proteins that turn operons on by –binding to DNA and –making it easier for RNA polymerase to bind to the promoter.  Activators help control a wide variety of operons. © 2012 Pearson Education, Inc.

15. 11.2 Chromosome structure and chemical modifications can affect gene expression  Differentiation –involves cell specialization, in structure and function, and –is controlled by turning specific sets of genes on or off.  Almost all of the cells in an organism contain an identical genome.  The differences between cell types are –not due to the presence of different genes but instead –due to selective gene expression. © 2012 Pearson Education, Inc.

16. 11.2 Chromosome structure and chemical modifications can affect gene expression  Eukaryotic chromosomes undergo multiple levels of folding and coiling, called DNA packing. –Nucleosomes are formed when DNA is wrapped around histone proteins. –This packaging gives a “beads on a string” appearance. –Each nucleosome bead includes DNA plus eight histones. –Stretches of DNA, called linkers, join consecutive nucleosomes. –At the next level of packing, the beaded string is wrapped into a tight helical fiber. –This fiber coils further into a thick supercoil. –Looping and folding can further compact the DNA. © 2012 Pearson Education, Inc.

17. 11.2 Chromosome structure and chemical modifications can affect gene expression  DNA packing can prevent gene expression by preventing RNA polymerase and other transcription proteins from contacting the DNA.  Cells seem to use higher levels of packing for long-term inactivation of genes.  Highly compacted chromatin, found in varying regions of interphase chromosomes, is generally not expressed at all. © 2012 Pearson Education, Inc. Animation: DNA Packing

18. 11.2 Chromosome structure and chemical modifications can affect gene expression  Chemical modification of DNA bases or histone proteins can result in epigenetic inheritance. –Certain enzymes can add a methyl group to DNA bases, without changing the sequence of the bases. –Individual genes are usually more methylated in cells in which the genes are not expressed. Once methylated, genes usually stay that way through successive cell divisions in an individual. © 2012 Pearson Education, Inc.

19. 11.2 Chromosome structure and chemical modifications can affect gene expression –Removal of the extra methyl groups can turn on some of these genes. –Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence is called epigenetic inheritance. These modifications can be reversed by processes not yet fully understood. © 2012 Pearson Education, Inc.

20. 11.2 Chromosome structure and chemical modifications can affect gene expression  X-chromosome inactivation –In female mammals, one of the two X chromosomes is highly compacted and transcriptionally inactive. –Either the maternal or paternal chromosome is randomly inactivated. –Inactivation occurs early in embryonic development, and all cellular descendants have the same inactivated chromosome. –An inactivated X chromosome is called a Barr body. –Tortoiseshell fur coloration is due to inactivation of X chromosomes in heterozygous female cats. © 2012 Pearson Education, Inc.

21. Figure 11.2A DNA double helix (2-nm diameter) “Beads on a string” Linker Histones Supercoil (300-nm diameter) Nucleosome (10-nm diameter) Tight helical fiber (30-nm diameter) Metaphase chromosome 700 nm

22. Figure 11.2A_1 “Beads on a string” Linker

23. Figure 11.2A_2 Metaphase chromosome 700 nm

24. Figure 11.2B Cell division and random X chromosome inactivation Early Embryo Adult X chromo- somes Allele for orange fur Allele for black fur Two cell populations Active X Inactive X Active X Inactive X Black fur Orange fur

25. Figure 11.2B_2

26. Figure 11.2B_1 Cell division and random X chromosome inactivation Early Embryo Adult X chromo- somes Allele for orange fur Allele for black fur Two cell populations Active X Inactive X Active X Inactive X Black fur Orange fur

27. 11.3 Complex assemblies of proteins control eukaryotic transcription  Prokaryotes and eukaryotes employ regulatory proteins (activators and repressors) that –bind to specific segments of DNA and –either promote or block the binding of RNA polymerase, turning the transcription of genes on and off.  In eukaryotes, activator proteins seem to be more important than repressors. Thus, the default state for most genes seems to be off.  A typical plant or animal cell needs to turn on and transcribe only a small percentage of its genes. © 2012 Pearson Education, Inc.

28. 11.3 Complex assemblies of proteins control eukaryotic transcription  Eukaryotic RNA polymerase requires the assistance of proteins called transcription factors. Transcription factors include –activator proteins, which bind to DNA sequences called enhancers and initiate gene transcription. The binding of the activators leads to bending of the DNA. –Other transcription factor proteins interact with the bound activators, which then collectively bind as a complex at the gene’s promoter.  RNA polymerase then attaches to the promoter and transcription begins. © 2012 Pearson Education, Inc. Animation: Initiation of Transcription

29. Figure 11.3 Enhancers DNA Promoter Gene Transcription factors Activator proteins Other proteins RNA polymerase Bending of DNA Transcription

30. 11.3 Complex assemblies of proteins control eukaryotic transcription  Silencers are repressor proteins that –may bind to DNA sequences and –inhibit transcription.  Coordinated gene expression in eukaryotes often depends on the association of a specific combination of control elements with every gene of a particular metabolic pathway. © 2012 Pearson Education, Inc.

31. 11.4 Eukaryotic RNA may be spliced in more than one way  Alternative RNA splicing –produces different mRNAs from the same transcript, –results in the production of more than one polypeptide from the same gene, and –may be common in humans. © 2012 Pearson Education, Inc. Animation: RNA Processing

32. Figure 11.4 DNA RNA transcript mRNA Exons Introns Cap Tail RNA splicing or 1 1 1 1 2 2 22 4 4 4 5 5 55 3 3 3

33. 11.5 Small RNAs play multiple roles in controlling gene expression  Only about 1.5% of the human genome codes for proteins. (This is also true of many other multicellular eukaryotes.)  Another small fraction of DNA consists of genes for ribosomal RNA and transfer RNA.  A flood of recent data suggests that a significant amount of the remaining genome is transcribed into functioning but non-protein-coding RNAs, including a variety of small RNAs. © 2012 Pearson Education, Inc.

34. 11.5 Small RNAs play multiple roles in controlling gene expression  microRNAs (miRNAs) can bind to complementary sequences on mRNA molecules either –degrading the target mRNA or –blocking its translation.  RNA interference (RNAi) is the use of miRNA to artificially control gene expression by injecting miRNAs into a cell to turn off a specific gene sequence. © 2012 Pearson Education, Inc. Animation: mRNA Degradation Animation: Blocking Translation

35. Figure 11.5 miRNA Target mRNA mRNA degraded or Translation blocked miRNA- protein complex Protein 3214

36. 11.6 Later stages of gene expression are also subject to regulation  After mRNA is fully processed and transported to the cytoplasm, gene expression can still be regulated by –breakdown of mRNA, –initiation of translation, –protein activation, and –protein breakdown. © 2012 Pearson Education, Inc.

37. Figure 11.6 Folding of the polypeptide and the formation of S—S linkages Initial polypeptide (inactive) Folded polypeptide (inactive) Active form of insulin Cleavage S S S S S S S S S S S S SH

38. 11.7 Review: Multiple mechanisms regulate gene expression in eukaryotes  Multiple control points exist where gene expression in eukaryotes can be –turned on or off or –speeded up, or slowed down.  These control points are like a series of pipes carrying water from your local water supply to a faucet in your home. Valves in this series of pipes are like the control points in gene expression. © 2012 Pearson Education, Inc. Animation: Protein Processing Animation: Protein Degradation

39. Figure 11.7 Chromosome DNA unpacking Other changes to the DNA Gene DNA Transcription Gene Exon Intron Tail Cap Addition of a cap and tail RNA transcript Splicing mRNA in nucleus NUCLEUS Flow through nuclear envelope mRNA in cytoplasm CYTOPLASM Breakdown of mRNA Translation Polypeptide Broken- down mRNA Cleavage, modification, activation Active protein Amino acids Breakdown of protein

40. 11.7 Review: Multiple mechanisms regulate gene expression in eukaryotes  These controls points include: 1.chromosome changes and DNA unpacking, 2.control of transcription, 3.control of RNA processing including the –addition of a cap and tail and –splicing, 4.flow through the nuclear envelope, 5.breakdown of mRNA, © 2012 Pearson Education, Inc.

41. 11.7 Review: Multiple mechanisms regulate gene expression in eukaryotes 6.control of translation, and 7.control after translation including –cleavage/modification/activation of proteins and –breakdown of protein. © 2012 Pearson Education, Inc.

42. 11.8 Cell signaling and cascades of gene expression direct animal development  Early research on gene expression and embryonic development came from studies of a fruit fly, revealing the control of these key events. 1.Orientation of the head-to-tail, top-to-bottom, and side-to- side axes are determined by early genes in the egg that produce proteins and maternal mRNAs. © 2012 Pearson Education, Inc. Animation: Development of Head-Tail Axis in Fruit Flies Animation: Cell Signaling

43. 11.8 Cell signaling and cascades of gene expression direct animal development 2.Segmentation of the body is influenced by cascades of proteins that diffuse through the cell layers. 3.Adult features develop under the influence of homeotic genes, master control genes that determine the anatomy of the parts of the body. © 2012 Pearson Education, Inc.

44. Figure 11.8A Antenna Eye Extra pair of legs

45. Figure 11.8B Egg cell within ovarian follicle Follicle cells “Head” mRNA Embryo Adult fly Expression of homeotic genes and cascades of gene expression Body segments Fertilization and mitosis Cascades of gene expression Gene expression Growth of egg cell Localization of “head” mRNA Egg cell Egg cell and follicle cells signaling each other 2 1 3 4

46. 11.9 CONNECTION: DNA microarrays test for the transcription of many genes at once  DNA microarrays help researchers study the expression of large groups of genes.  A DNA microarray –contains DNA sequences arranged on a grid and –is used to test for transcription in the following way: –mRNA from a specific cell type is isolated, –fluorescent cDNA is produced from the mRNA, –cDNA is applied to the microarray, –unbound cDNA is washed off, and –complementary cDNA is detected by fluorescence. © 2012 Pearson Education, Inc.

47. Figure 11.9 3 4 2 1 mRNA is isolated. Reverse transcriptase and fluorescent DNA nucleotides cDNA is made from mRNA. Unbound cDNA is rinsed away. cDNA is applied to the wells. DNA microarray Each well contains DNA from a particular gene. Fluorescent spot Nonfluorescent spot cDNA DNA of an expressed gene DNA of an unexpressed gene Actual size (6,400 genes)

48. 11.9 CONNECTION: DNA microarrays test for the transcription of many genes at once  DNA microarrays are a potential boon to medical research. –In 2002, a study showed that DNA microarray data can classify different types of leukemia, helping to identify which chemotherapies will be most effective. –Other research suggests that many cancers have a variety of subtypes with different gene expression patterns. –DNA microarrays also reveal general profiles of gene expression over the lifetime of an organism. © 2012 Pearson Education, Inc.

49. 11.10 Signal transduction pathways convert messages received at the cell surface to responses within the cell  A signal transduction pathway is a series of molecular changes that convert a signal on the target cell’s surface to a specific response within the cell.  Signal transduction pathways are crucial to many cellular functions. © 2012 Pearson Education, Inc. Animation: Signal Transduction Pathways Animation: Overview of Cell Signaling

50. Figure 11.10 3 2 1 4 5 6 Signaling cell EXTRACELLULAR FLUID Signaling molecule Receptor protein Plasma membrane Target cell Relay proteins Signal transduction pathway Transcription factor (activated) NUCLEUS DNA mRNA CYTOPLASM Transcription Translation New protein

51. CLONING OF PLANTS AND ANIMALS © 2012 Pearson Education, Inc.

52. 11.13 Nuclear transplantation can be used to clone animals  Animal cloning can be achieved using nuclear transplantation, in which the nucleus of an egg cell or zygote is replaced with a nucleus from an adult somatic cell.  Using nuclear transplantation to produce new organisms is called reproductive cloning. It was first used in mammals in 1997 to produce the sheep Dolly. © 2012 Pearson Education, Inc.

53. 11.13 Nuclear transplantation can be used to clone animals  Another way to clone uses embryonic stem (ES) cells harvested from a blastocyst. This procedure can be used to produce –cell cultures for research or –stem cells for therapeutic treatments. © 2012 Pearson Education, Inc.

54. Figure 11.13 The nucleus is removed from an egg cell. Donor cell A somatic cell from an adult donor is added. Nucleus from the donor cell Reproductive cloning Blastocyst The blastocyst is implanted in a surrogate mother. A clone of the donor is born. The cell grows in culture to produce an early embryo (blastocyst). Therapeutic cloning Embryonic stem cells are removed from the blastocyst and grown in culture. The stem cells are induced to form specialized cells.

55. Figure 11.13_1 The nucleus is removed from an egg cell. Donor cell A somatic cell from an adult donor is added. Nucleus from the donor cell Blastocyst The cell grows in culture to produce an early embryo (blastocyst).

56. Figure 11.13_2 Reproductive cloning Blastocyst The blastocyst is implanted in a surrogate mother. A clone of the donor is born. Therapeutic cloning Embryonic stem cells are removed from the blastocyst and grown in culture. The stem cells are induced to form specialized cells.

57. 11.14 CONNECTION: Reproductive cloning has valuable applications, but human reproductive cloning raises ethical issues  Since Dolly’s landmark birth in 1997, researchers have cloned many other mammals, including mice, cats, horses, cows, mules, pigs, rabbits, ferrets, and dogs.  Cloned animals can show differences in anatomy and behavior due to –environmental influences and –random phenomena. © 2012 Pearson Education, Inc.

58. 11.14 CONNECTION: Reproductive cloning has valuable applications, but human reproductive cloning raises ethical issues  Reproductive cloning is used to produce animals with desirable traits to –produce better agricultural products, –produce therapeutic agents, and –restock populations of endangered animals.  Human reproductive cloning raises many ethical concerns. © 2012 Pearson Education, Inc.

59. 11.15 CONNECTION: Therapeutic cloning can produce stem cells with great medical potential  When grown in laboratory culture, stem cells can –divide indefinitely and –give rise to many types of differentiated cells.  Adult stem cells can give rise to many, but not all, types of cells. © 2012 Pearson Education, Inc.

60. 11.15 CONNECTION: Therapeutic cloning can produce stem cells with great medical potential  Embryonic stem cells are considered more promising than adult stem cells for medical applications.  The ultimate aim of therapeutic cloning is to supply cells for the repair of damaged or diseased organs. © 2012 Pearson Education, Inc.

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

62. THE GENETIC BASIS OF CANCER © 2012 Pearson Education, Inc.

63. 11.16 Cancer results from mutations in genes that control cell division  Mutations in two types of genes can cause cancer. 1.Oncogenes –Proto-oncogenes are normal genes that promote cell division. –Mutations to proto-oncogenes create cancer-causing oncogenes that often stimulate cell division. 2.Tumor-suppressor genes –Tumor-suppressor genes normally inhibit cell division or function in the repair of DNA damage. –Mutations inactivate the genes and allow uncontrolled division to occur. © 2012 Pearson Education, Inc.

64. Figure 11.16A Oncogene Hyperactive growth- stimulating protein in a normal amount Normal growth- stimulating protein in excess New promoter The gene is moved to a new DNA locus, under new controls Multiple copies of the gene A mutation within the gene Proto-oncogene (for a protein that stimulates cell division) DNA

65. Figure 11.16B Tumor-suppressor gene Mutated tumor-suppressor gene Normal growth- inhibiting protein Cell division under control Defective, nonfunctioning protein Cell division not under control

66. 11.17 Multiple genetic changes underlie the development of cancer  Usually four or more somatic mutations are required to produce a full-fledged cancer cell.  One possible scenario is the stepwise development of colorectal cancer. 1.An oncogene arises or is activated, resulting in increased cell division in apparently normal cells in the colon lining. 2.Additional DNA mutations cause the growth of a small benign tumor (polyp) in the colon wall. 3.Additional mutations lead to a malignant tumor with the potential to metastasize. © 2012 Pearson Education, Inc.

67. Figure 11.17A Colon wall DNA changes: Cellular changes: Growth of a polyp An oncogene is activated Increased cell division A tumor-suppressor gene is inactivated A second tumor- suppressor gene is inactivated Growth of a malignant tumor 123

68. Figure 11.17B Chromosomes 1 mutation 2 mutations 3 mutations 4 mutations Normal cell Malignant cell

69. 11.18 Faulty proteins can interfere with normal signal transduction pathways  Proto-oncogenes and tumor-suppressor genes often code for proteins involved in signal transduction pathways leading to gene expression.  Two main types of signal transduction pathways lead to the synthesis of proteins that influence cell division. © 2012 Pearson Education, Inc.

70. 11.18 Faulty proteins can interfere with normal signal transduction pathways 1.One pathway produces a product that stimulates cell division. –In a healthy cell, the product of the ras proto- oncogene relays a signal when growth factor binds to a receptor. –But in a cancerous condition, the product of the ras proto-oncogene relays the signal in the absence of a growth factor, leading to uncontrolled growth. –Mutations in ras occur in more than 30% of human cancers. © 2012 Pearson Education, Inc.

71. Figure 11.18A Growth factor Target cell Normal product of ras gene Relay proteins Receptor Hyperactive relay protein (product of ras oncogene) issues signals on its own CYTOPLASM DNA NUCLEUS Transcription Translation Protein that stimulates cell division Transcription factor (activated)

72. 11.18 Faulty proteins can interfere with normal signal transduction pathways 2.A second pathway produces a product that inhibits cell division. –The normal product of the p53 gene is a transcription factor that normally activates genes for factors that inhibit cell division. –In the absence of functional p53, cell division continues because the inhibitory protein is not produced. –Mutations in p53 occur in more than 50% of human cancers. © 2012 Pearson Education, Inc.

73. Figure 11.18B Growth-inhibiting factor Receptor Relay proteins Transcription factor (activated) Nonfunctional transcription factor (product of faulty p53 tumor-suppressor gene) cannot trigger transcription Normal product of p53 gene Transcription Translation Protein that inhibits cell division Protein absent (cell division not inhibited)

74. 11.19 CONNECTION: Lifestyle choices can reduce the risk of cancer  After heart disease, cancer is the second-leading cause of death in most industrialized nations.  Cancer can run in families if an individual inherits an oncogene or a mutant allele of a tumor-suppressor gene that makes cancer one step closer.  But most cancers cannot be associated with an inherited mutation. © 2012 Pearson Education, Inc.

75. 11.19 CONNECTION: Lifestyle choices can reduce the risk of cancer  Carcinogens are cancer-causing agents that alter DNA.  Most mutagens (substances that promote mutations) are carcinogens.  Two of the most potent carcinogens (mutagens) are –X-rays and –ultraviolet radiation in sunlight. © 2012 Pearson Education, Inc.

76. 11.19 CONNECTION: Lifestyle choices can reduce the risk of cancer  The one substance known to cause more cases and types of cancer than any other single agent is tobacco. –More people die of lung cancer than any other form of cancer. –Although most tobacco-related cancers come from smoking, passive inhalation of second-hand smoke is also a risk. –Tobacco use, sometimes in combination with alcohol consumption, causes cancers in addition to lung cancer. © 2012 Pearson Education, Inc.

77. 11.19 CONNECTION: Lifestyle choices can reduce the risk of cancer  Healthy lifestyles that reduce the risks of cancer include –avoiding carcinogens, including the sun and tobacco products, –exercising adequately, –regular medical checks for common types of cancer, and –a healthy high-fiber, low-fat diet including plenty of fruits and vegetables. © 2012 Pearson Education, Inc.

78. Table 11.19

79. 1.Describe and compare the regulatory mechanisms of the lac operon, trp operon, and operons using activators. 2.Explain how selective gene expression yields a variety of cell types in multicellular eukaryotes. 3.Explain how DNA is packaged into chromosomes. 4.Explain how a cat’s tortoiseshell coat pattern is formed and why this pattern is only seen in female cats. You should now be able to © 2012 Pearson Education, Inc.

80. 5.Explain how eukaryotic gene expression is controlled. 6.Describe the process and significance of alternative DNA splicing. 7.Describe the significance of miRNA molecules. 8.Explain how mRNA breakdown, initiation of translation, protein activation, and protein breakdown regulate gene expression. You should now be able to © 2012 Pearson Education, Inc.

81. 9.Describe the roles of homeotic genes in development. 10.Explain how DNA microarrays can be used to study gene activity and treat disease. 11.Explain how a signal transduction pathway triggers a specific response inside a target cell. 12.Compare the cell-signaling systems of yeast and animal cells. You should now be able to © 2012 Pearson Education, Inc.

82. 13.Explain how nuclear transplantation can be used to clone animals. 14.Describe some of the practical applications of reproductive cloning and the process and goals of therapeutic cloning. 15.Explain how viruses, proto-oncogenes, and tumor-suppressor genes can each contribute to cancer. 16.Explain why the development of most cancers is a slow and gradual process. You should now be able to © 2012 Pearson Education, Inc.

83. 17.Explain how mutations in ras or p53 proteins can lead to cancer. 18.Describe factors that can increase or decrease the risks of developing cancer. You should now be able to © 2012 Pearson Education, Inc.

84. Figure 11.UN01 A typical operon DNA Regulatory gene Promoter Operator Gene 1 Gene 2 Gene 3 Encodes a repressor that in active form attaches to an operator RNA polymerase binding site Switches the operon on or off Code for proteins

85. Figure 11.UN02 Egg cell or zygote with nucleus removed Nucleus from a donor cell An early embryo resulting from nuclear trans- plantation Surrogate mother Clone of the donor

86. Figure 11.UN03 Egg cell or zygote with nucleus removed Nucleus from a donor cell An early embryo resulting from nuclear trans- plantation Embryonic stem cells in culture Specialized cells

87. Figure 11.UN04 Gene regulation operons oncogene female mammals multiple kinds of mRNA per gene transcription prokaryotic genes are often grouped into in eukaryotes may involve when abnormal may lead to is a normal gene that can be mutated to an controlled by a protein called are switched on/off by in active form binds to are proteins that promote can cause can produce occurs in (a) (b) (c) (d) (e)(f) (g)