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Biology Chapter 12 DNA and RNA Unit 12.1 Unit 12.2 Unit 12.3 Unit 12.4
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DNA In class assignment.
1. Draw four different symbols (i.e. Ω ∆ π ). 2. Write down any five letter word. 3. Develop a code for the five letters of that word using only your four symbols. How can you code for five different letters with only four different symbols? 4.How many different letters can you code for using only two of your symbols to stand for each letter. 5. How many different letters could you code for using a string of three symbols for each letter?
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WHAT IS THE CHEMICAL NATURE OF THE GENE?
DNA Essential Questions of mid 1900’s How do genes work? What are they made of? Are genes single molecules or longer structures made up of many molecules? WHAT IS THE CHEMICAL NATURE OF THE GENE?
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DNA 1928 Frederick Griffith - How do pneumonia make people sick?
Two strains of bacteria smooth strain - caused disease rough edges - no disease
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DNA Griffith’s Experiment Thought that poison killed mice
1928 Frederick Griffith - How do pneumonia make people sick? Two strains of bacteria smooth strain - caused disease rough edges - no disease Griffith’s Experiment Thought that poison killed mice But heat-killed smooth bacteria didn’t kill mice Transformation Griffith mixed dead smooth cell bacteria with live rough bacteria Mice died Somehow the rough bacteria had been transformed
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DNA Heat-killed, disease-causing bacteria (smooth colonies)
Harmless bacteria (rough colonies) Harmless bacteria (rough colonies) Heat-killed, disease-causing bacteria (smooth colonies) Control (no growth) Disease-causing bacteria (smooth colonies)
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DNA Heat-killed, disease-causing bacteria (smooth colonies)
Harmless bacteria (rough colonies) Control (no growth) Harmless bacteria (rough colonies) Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies)
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DNA Avery and DNA Repeated Griffith’s experiment
Thought that poison killed mice But heat-killed smooth bacteria didn’t kill mice Transformation Griffith mixed dead smooth cell bacteria with live rough bacteria; Mice died Somehow the rough bacteria had been transformed Avery and DNA Repeated Griffith’s experiment Treated extract with enzymes to destroy proteins, lipids, carbohydrates, RNA Transformation still occurred Finally broke down DNA No transformation occurred
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DNA HERSHEY-CHASE EXPERIMENT 1952 Alfred Hershey & Martha Chase
Avery and DNA Repeated Griffith’s experiment Treated extract with enzymes to destroy proteins, lipids, carbohydrates, RNA Transformation still occurred Finally broke down DNA; no transformation occurred AVERY AND OTHERS DISCOVERED THAT DNA STORES AND TRANSMITS GENETIC INFORMATION HERSHEY-CHASE EXPERIMENT 1952 Alfred Hershey & Martha Chase Bacteriophages (bacteria eaters) Used radioactive markers phosphorus-32 and sulfur-35 Phosphorus only in DNA, Sulfur only in protein Showed DNA, not protein was genetic material
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DNA
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DNA Structure of DNA •Must carry genetic information to new generations •Must be easily copied Polymer DNA Monomer - nucleotide deoxyribose (sugar) phosphate group nitrogenous base adenine & guanine are purines cytosine & thymine are pyrimidines By early 1950’s scientists wondered how DNA, just a string of nucleotides could be the genetic code
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DNA Structure of nucleotides Purines Pyrimidines Adenine Guanine
Cytosine Thymine Deoxyribose Phosphate group
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DNA Chargaff’s Rule Erwin Chargaff discovered
Source of DNA A T G C Streptococcus Yeast Herring Human Erwin Chargaff discovered •percentages of G and C are almost equal •percentages of A and T are almost equal
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DNA X-Ray Evidence Early 1950’s Rosalind Franklin X-ray diffraction
Chargaff’s Rule Erwin Chargaff discovered •percentages of G and C are almost equal •percentages of A and T are almost equal X-Ray Evidence Early 1950’s Rosalind Franklin X-ray diffraction X-shaped pattern showed twisted or helix shape
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DNA BASE PAIRING - explained Chargaff’s rule A bonds to T G bonds to C
The Double Helix Francis Crick and James Watson Made cardboard and wire models When they say Franklin’s X-ray pattern the light came on: Credited with the double-helix model Two strands wound around each other BASE PAIRING - explained Chargaff’s rule A bonds to T G bonds to C
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DNA Base Pairing Key Nucleotide Adenine (A) Thymine (T) Cytosine (C)
Guanine (G) Sugar-phosphate backbone Nucleotide
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DNA Base Pairing Nucleotide Key Adenine (A) Thymine (T) Cytosine (C)
Page 294 Base Pairing Nucleotide Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Sugar-phosphate backbone
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DNA The Double Helix Francis Crick and James Watson, 1953
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DNA The Double Helix Nucleotide Hydrogen bonds Page 294
Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)
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12.2Chromosomes and RNA Replication
Goals Summarize the events of DNA replication Relate the DNA molecule to chromosome structure
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12.2Chromosomes and RNA Replication
DNA and Chromosomes Prokaryotes: One circular DNA molecule
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12.2Chromosomes and RNA Replication
DNA and Chromosomes Prokaryotes: One circular DNA molecule Eukaryotes: 1,000 times as much DNA DNA found in nucleus Organized into chromosomes 46 in human beings 8 in drosophila 22 in redwood trees
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12.2Chromosomes and RNA Replication
DNA length E. Coli 4,639,221 base pairs 1.6 millimeters inside a 1.6µm (1/1,000 of a mm) imagine 1m yarn inside 1mm ball
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12.2Chromosomes and RNA Replication
Chromosome Structure Eukaryote DNA packed more tightly Human chromosome > 30 million base pairs A human cell has more than 1METER of DNA! How does it all fit?
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12.2Chromosomes and RNA Replication
Chromosome Structure A human cell has more than 1METER of DNA! How does it all fit? DNA and protein(histones) pack together into bead-like nucleosomes which coil into tight loops and coils chromatin Chromatin is dispersed until cell division when chromosomes form
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12.2Chromosomes and RNA Replication
Chromosome Structure A human cell has more than 1METER of DNA! How does it all fit? DNA and protein(histones) pack together into bead-like nucleosomes which coil into tight loops and coils chromatin Chromatin is dispersed until cell division when chromosomes form
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12.2Chromosomes and RNA Replication
DNA Replication Two strands are, “complimentary” You could construct one strand from the other (remember base-pairing) DNA separates into two strands Each strand is a model for a duplicate complimentary strand
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12.2Chromosomes and RNA Replication
DNA Replication DNA separates into two strands Each strand is a model for a duplicate complimentary strand Enzymes unzip the molecule DNA polymerase Nucleotides are arranged on the template strand.
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12.2Chromosomes and RNA Replication
DNA Replication Page 298
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Quiz 1 15 points 3 questions 5 points for each question You will need a piece of paper and a pen or pencil. Get those out now. You may use your notes; please put books neatly away This paper must have a standard heading at the top of the page, full name, date, and period Yes, neatness does count. Drawings must be clearly labeled
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1. Make a drawing or several drawings of DNA that demonstrate your understanding of its basic structure. Be sure to include and label the sugar-phosphate backbone, base pairing and double helix. Correctly show the relationship between the Adenine, Thymine, Guanine, and Cytosine 2. Make a labeled drawing and explain how DNA is replicated 3. Describe one of the experiments that demonstrated that DNA is the substance that carries genetic information.
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12.RNA and Protein Synthesis
Essential Questions •How does RNA differ from DNA? •What are the different types of RNA? •What is transcription of RNA? •What is the genetic code? •Explain translation •What is the relationship between genes and protein? Click for a great animation
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12.RNA and Protein Synthesis
A part of the genetic code is copied from DNA to mRNA RNA carries out process of making proteins
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12.RNA and Protein Synthesis
“The Central Dogma” The information encoded with the DNA nucleotide sequence of a double helix is transferred to a mRNA molecule. The mRNA molecule travels out of the nucleus and attaches to a ribosome Using the RNA nucleotide sequence and the genetic code, the ribosome assembles a protein
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12.RNA and Protein Synthesis
TRANSCRIPTION DNA stays in the nucleus mRNA is copied from DNA and sent out into the cytoplasm Animations: Transcription showing full complex Transcription – cool sounds
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12.RNA and Protein Synthesis
The Central Dogma (brief) DNA is copied to mRNA mRNA is used as blueprint to make protein
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12.RNA and Protein Synthesis
Structure of RNA RNA’s sugar backbone contains ribose instead of deoxyribose RNA is like one strand of the DNA double-helix RNA uses uracil instead of Thymine
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12.RNA and Protein Synthesis
RNA’s sugar backbone contains ribose instead of deoxyribose RNA is like one strand of the DNA double-helix RNA uses uracil instead of Thymine Types of RNA PROTEIN SYNTHESIS •Messenger RNA brings a copy of gene code from nucleus to cytoplasm Ribosomal RNA Transfer RNA transfers code to protein
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12.RNA and Protein Synthesis
•Messenger RNA brings a copy of gene code from nucleus to cytoplasm Ribosomal RNA Transfer RNA transfers code to protein Transcription •RNA polymerase separates strands makes a transcript of one strand on mRNA Promoters tell RNA polymerase where to start transcribing
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tRNA tRNA - transfer Specified amino acids are attached to tRNA
each anti-codon corresponds to the amino acid specified by the genetic code Each tRNA has an anti-codon (3 nucleotides) Anti-codon region base pairs with mRNA trascript
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12.RNA and Protein Synthesis
RNA polymerase separates strands makes a transcript of one strand on mRNA Promoters tell RNA plymerase where to start transcribing Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase DNA RNA
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12.RNA and Protein Synthesis
RNA polymerase separates strands makes a transcript of one strand on mRNA Promoters tell RNA plymerase where to start transcribing RNA Editing Some editing takes place once RNA is transcribed •Introns - sections of mRNA to are cut out •Exons - spliced back together to form final mRNA
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12.RNA and Protein Synthesis
•Introns - sections of mRNA to are cut out •Exons - spliced back together to form final mRNA Genetic Code Polymer - protein Monomer - amino acid (there are 20 possibilities) codon - 3 nucleotides codes for each amino acid
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12.RNA and Protein Synthesis
Polymer - protein Monomer - amino acid (there are 20 possibilities) 3 nucleotides = 1 codon - codes for each amino acid Translation Assembly happens in ribosome Transfer RNA anticodon matches to mRNA codon and brings attached amino acid Polypeptide chain grows until STOP codon is reached
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12.RNA and Protein Synthesis
Assembly happens in ribosome Transfer RNA anticodon matches to mRNA codon and brings attached amino acid Polypeptide chain grows until STOP codon is reached
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12.RNA and Protein Synthesis
Assembly happens in ribosome Transfer RNA anticodon matches to mRNA codon and brings attached amino acid Polypeptide chain grows until STOP codon is reached
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12.RNA and Protein Synthesis
Assembly happens in ribosome Transfer RNA anticodon matches to mRNA codon and brings attached amino acid Polypeptide chain grows until STOP codon is reached Roles of DNA / RNA DNA - master plan kept safe in nucleus RNA - working blueprints brought out to cytoplasm
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12.RNA and Protein Synthesis
DNA - master plan kept safe in nucleus RNA - working blueprints brought out to cytoplasm Genes and Proteins Genes code proteins Proteins are enzymes catalyze chemical reactions Color, antigens, blood type Proteins are the key
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12.RNA and Protein Synthesis
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12.RNA and Protein Synthesis animations
Translation Translation – no sound, basic
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Four Roles •DNA - Agent DiNA Provides code to be broken
CODE Breaker Activity Four Roles •DNA - Agent DiNA Provides code to be broken •mRNA - Agent miRNA Translates code for Agent tuRNA •tRNA - Agent tuRNA picks up code delivers it to •rRNA - Agent R.B.Some compiles information
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Step 1 DNA - Agent DiNA •counts 3 numbers starting from left
CODE Breaker Activity Step 1 DNA - Agent DiNA •counts 3 numbers starting from left •cuts 1 group •passes it off to Agent miRNA •only 1 group of 3 may be cut at a time
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CODE Breaker Activity Step 2 mRNA - Agent miRNA • Using secret table code, Agent miRNA decodes and translates to a letter •Relays letter information to Agent tuRNA
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Step 3 tRNA - Agent tuRNA • Gets letter information from Agent miRNA
CODE Breaker Activity Step 3 tRNA - Agent tuRNA • Gets letter information from Agent miRNA •Turns letter over to R.B.Some
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Step 3 R.B.Some • Assembles letters After step four is completed,
CODE Breaker Activity Step 3 R.B.Some • Assembles letters After step four is completed, REPEAT Until code is broken
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Cells make mistakes 12.4 Mutations
1. Copy the following information about Protein X: Methionine—Phenylalanine—Tryptophan—Asparagine—Isoleucine—STOP. 2. Use Figure 12–17 on page 303 in your textbook to determine one possible sequence of RNA to code for this information. Write this code below the description of Protein X. Below this, write the DNA code that would produce this RNA sequence. 3. Now, cause a mutation in the gene sequence that you just determined by deleting the fourth base in the DNA sequence. Write this new sequence. 4. Write the new RNA sequence that would be produced. Below that, write the amino acid sequence that would result from this mutation in your gene. Call this Protein Y. 5. Did this single deletion cause much change in your protein? Explain your answer.
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Mutate - to change Cells make mistakes
12.4 Mutations Cells make mistakes Mutate - to change •Gene mutations are changes in a single gene •Chromosomal mutations involve changes in whole chromosomes
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change in one nucleotide •Substitution changes 1 amino acid
12.4 Mutations Gene Mutations Point mutations change in one nucleotide •Substitution changes 1 amino acid •Frameshift mutation insertion or deletion of one nucleotide throws off subsequent codons can prevent functioning of gene
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12.4 Mutations Gene Mutations
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12.4 Mutations Gene Mutations
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Change in number or structure of chromosomes •deletion •duplication
12.4 Mutations Chromosomal Mutations Change in number or structure of chromosomes •deletion •duplication •inversion •translocation
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12.5 Gene Regulation Every cell in your body, with the exception of gametes, or sex cells, contains a complete copy of your DNA. Why, then, are some cells nerve cells with dendrites and axons, while others are red blood cells that have lost their nuclei and are packed with hemoglobin? Why are cells so different in structure and function? If the characteristics of a cell depend upon the proteins that are synthesized, what does this tell you about protein synthesis? Answer the questions that follow: 1. Do you think that cells produce all the proteins for which the DNA (genes) code? Why or why not? How do the proteins made affect the type and function of cells? 2. Consider what you now know about genes and protein synthesis. What might be some ways that a cell has control over the proteins it produces? 3. What type(s) of organic compounds are most likely the ones that help to regulate protein synthesis? Justify your answer.
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12.5 Gene Regulation Every cell in your body, with the exception of gametes, or sex cells, contains a complete copy of your DNA. Why, then, are some cells nerve cells with dendrites and axons, while others are red blood cells that have lost their nuclei and are packed with hemoglobin? Why are cells so different in structure and function? If the characteristics of a cell depend upon the proteins that are synthesized, what does this tell you about protein synthesis? Answer the questions that follow: 1. Do you think that cells produce all the proteins for which the DNA (genes) code? Why or why not? How do the proteins made affect the type and function of cells? 2. Consider what you now know about genes and protein synthesis. What might be some ways that a cell has control over the proteins it produces? 3. What type(s) of organic compounds are most likely the ones that help to regulate protein synthesis? Justify your answer.
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Describe a typical gene
12.5 Gene Regulation Goals Describe a typical gene Describe how the lac genes are turned on and off Explain how most eukaryotic genes are controlled Relate gene regulation to development
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Not every gene is expressed in every cell
12.5 Gene Regulation Gene Expression Not every gene is expressed in every cell Cells in your finger don’t produce amylase Promoters tell RNA to start transcription What are the regulatory sites next to the promoter ?
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Gene Regulation: An Example the lac operon
Gene Expression Not every gene is expressed in every cell Cells in your finger don’t produce amylase Promoters tell RNA to start transcription What are the regulatory sites next to the promoter ? Gene Regulation: An Example the lac operon In E. coli 3 genes are turned on and off together Operon - genes that operate together These 3 genes help E. coli use lactose - lac operon
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12.5 Gene Regulation Gene Regulation: An Example the lac operon
In E. coli 3 genes are turned on and off together Operon - genes that operate together These 3 genes help E. coli use lactose - lac operon Lac operon codes for proteins that take lactose across the cell membrane break lactose up into galactose and glucose The lac operon genes are turned on by the presence of lactose Beside the 3 lac operon genes are two other regions Promoter Operator
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12.5 Gene Regulation Lac operon codes for proteins that take lactose across the cell membrane break lactose up into galactose and glucose The lac operon genes are turned on by the presence of lactose Beside the 3 lac operon genes are two other regions Promoter Operator When RNA polymerase gets to the promoter, it transcriptions begins The operator blocks it by binding to a protein called the lac repressor BUT if lactose binds to the repressor, it falls off allowing RNA polymerase to begin transcription
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12.5 Gene Regulation Eukaryotic Gene Regulation Operons are not used
When RNA polymerase gets to the promoter, it transcriptions begins The operator blocks it by binding to a protein called the lac repressor BUT if lactose binds to the repressor, it falls off allowing RNA polymerase to begin transcription Eukaryotic Gene Regulation Operons are not used Genes are controlled individually Regulatory sequences more complex than lac TATATA or TATAAA region “TATA Box” helps position RNA polymerase Found just before eukaryotic promoters
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12.5 Gene Regulation Many, “enhancer,” sequences found in eukaryotes
Eukaryotic Gene Regulation Operons are not used Genes are controlled individually Regulatory sequences more complex than lac TATATA or TATAAA region “TATA Box” helps position RNA polymerase Found just before eukaryotic promoters Many, “enhancer,” sequences found in eukaryotes •unwind tightly twisted chromatin •attract RNA polymerase •block access (like prokaryote repressor proteins)
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12.5 Gene Regulation Many, “enhancer,” sequences found in eukaryotes
•unwind tightly twisted chromatin •attract RNA polymerase •block access (like prokaryote repressor proteins) Regulatory sites Promoter (RNA polymerase binding site) DNA strand Start transcription Stop transcription
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12.5 Gene Regulation WHY IS THE SYSTEM SO COMPLEX IN EUKARYOTES
Many, “enhancer,” sequences found in eukaryotes •unwind tightly twisted chromatin •attract RNA polymerase •block access (like prokaryote repressor proteins) WHY IS THE SYSTEM SO COMPLEX IN EUKARYOTES •Complex multicellular organisms •All cells carry the code •Each cell uses only a tiny fraction of the code
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12.5 Gene Regulation Regulation and Development
WHY IS THE SYSTEM SO COMPLEX IN EUKARYOTES •Complex multicellular organisms •All cells carry the code •Each cell uses only a tiny fraction of the code Regulation and Development “hox genes” control embryo development Which cells develop into what Master control genes Fruit fly legs growing in the place of antennae Copy of mouse eye growth gene inserted into drosophila leg caused fruit fly to grow an eye on its knee! Onward to Genetic Engineering next week
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