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Chapter 12: D NA and RNA. KWL Chart What I KNOW already about DNA What I WANT to know about DNA What I have LEARNED about DNA.

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Presentation on theme: "Chapter 12: D NA and RNA. KWL Chart What I KNOW already about DNA What I WANT to know about DNA What I have LEARNED about DNA."— Presentation transcript:

1 Chapter 12: D NA and RNA

2 KWL Chart What I KNOW already about DNA What I WANT to know about DNA What I have LEARNED about DNA

3 Learning Targets for Section 12-1 Summarize the relationship between genes and DNA?Summarize the relationship between genes and DNA? Describe the overall structure of DNA?Describe the overall structure of DNA?

4 12–1 Research Behind DNA Griffith and Transformation  In 1928, British scientist Frederick Griffith tried to determine which bacteria produced pneumonia. Griffith isolated two different strains.Griffith isolated two different strains. 1. disease-causing = smooth colonies 2. harmless strain = rough colonies.

5 Griffith's Experiment Griffith's Experiment Griffith injected miceGriffith injected mice 1. disease-causing bacteria- mice developed pneumonia and died. 2. harmless strain - didn’t get sick at all

6 Experiment cont. Experiment cont. Griffith’s then mixed heat-killed, disease-causing bacteria with live, harmless ones and injected the mixture into miceGriffith’s then mixed heat-killed, disease-causing bacteria with live, harmless ones and injected the mixture into mice Mice developed pneumonia and many died.Mice developed pneumonia and many died. Found their lungs filled with the disease- causing bacteriaFound their lungs filled with the disease- causing bacteria

7 Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease- causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumoniaLives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia Section 12-1 Figure 12–2 Griffith’s Experiment Go to Section:

8 Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease- causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumoniaLives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia Section 12-1 Figure 12–2 Griffith’s Experiment Go to Section:

9 Disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease- causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumoniaLives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia Section 12-1 Figure 12–2 Griffith’s Experiment Go to Section:

10 Griffith’s Conclusion: Griffith hypothesized some factor transformed harmless cells into the heat-killed harmful cellsGriffith hypothesized some factor transformed harmless cells into the heat-killed harmful cells Griffith movie

11 Avery and DNA Avery and his colleagues repeated Griffith’s experiment then:Avery and his colleagues repeated Griffith’s experiment then: Used enzymes that destroyed proteins, lipids, carbohydrates, and other molecules, including the nucleic acid RNAUsed enzymes that destroyed proteins, lipids, carbohydrates, and other molecules, including the nucleic acid RNA When they destroyed the nucleic acid (DNA), transformation did not occurWhen they destroyed the nucleic acid (DNA), transformation did not occur

12 Avery’s Conclusion: Avery and other scientists discovered that DNA is the nucleic acid that stores and transmits the genetic information from one generation of an organism to the nextAvery and other scientists discovered that DNA is the nucleic acid that stores and transmits the genetic information from one generation of an organism to the next

13 The Hershey Chase Experiment Martha Chase and Alfred HersheyMartha Chase and Alfred Hershey

14 The Hershey Chase Experiment Studied viruses, nonliving particles smaller than a cell that can infect living organismsStudied viruses, nonliving particles smaller than a cell that can infect living organisms Hershey and Chase reasoned that if they could determine which part of the virus—the protein coat or the DNA core—entered the infected cell, they would learn whether genes were made of protein or DNAHershey and Chase reasoned that if they could determine which part of the virus—the protein coat or the DNA core—entered the infected cell, they would learn whether genes were made of protein or DNA They grew viruses in cultures of radioactive isotopes of phosphorus-32 (32P) and sulfur-35 (35S).They grew viruses in cultures of radioactive isotopes of phosphorus-32 (32P) and sulfur-35 (35S).

15 Proteins contain almost no phosphorus and DNA contains no sulfurProteins contain almost no phosphorus and DNA contains no sulfur If 35S was found in the bacteria, it would mean that the viruses’ protein had been injected, If 32P was found in the bacteria, then it was the DNA that had been injectedIf 35S was found in the bacteria, it would mean that the viruses’ protein had been injected, If 32P was found in the bacteria, then it was the DNA that had been injected The Hershey Chase Experiment

16 Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Figure 12–4 Hershey-Chase Experiment Section 12-1 Go to Section:

17 Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Figure 12–4 Hershey-Chase Experiment Section 12-1 Go to Section:

18 Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Figure 12–4 Hershey-Chase Experiment Section 12-1 Go to Section:

19 Hershey and Chase’s Conclusion : Hershey and Chase concluded that the genetic material of the bacteriophage was DNA, not protein.

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21 REVIEW In your science journal:In your science journal: List as many scientists you can rememberList as many scientists you can remember And describe their contribution to our understanding of DNAAnd describe their contribution to our understanding of DNA

22 The Structure of DNA DNA is a long molecule made up of units called nucleotidesDNA is a long molecule made up of units called nucleotides Each nucleotide is made up of three parts:Each nucleotide is made up of three parts: 1. a 5-carbon sugar called deoxyribose, 2. a phosphate group, 3. and a nitrogenous (nitrogen-containing) base

23 There are four kinds of nitrogenous bases in DNA Purines:Purines: Adenine: Expressed AAdenine: Expressed A Guanine: Expressed GGuanine: Expressed G Pyrimidines:Pyrimidines: Thymine: Expressed TThymine: Expressed T Cytocine: Expressed CCytocine: Expressed C

24 PurinesPyrimidines AdenineGuanineCytosineThymine Phosphate group Deoxyribose Figure 12–5 DNA Nucleotides Section 12-1 Go to Section:

25 Chargaff’s Rules Erwin Chargaff, an American biochemist, discovered that the percentages of guanine [G] and cytosine [C] are almost equal in any sample of DNAErwin Chargaff, an American biochemist, discovered that the percentages of guanine [G] and cytosine [C] are almost equal in any sample of DNA The same thing is true for adenine [A] and thymine [T]The same thing is true for adenine [A] and thymine [T] Despite the fact that DNA samples from organisms obeyed this rule, neither Chargaff nor anyone else had the faintest idea whyDespite the fact that DNA samples from organisms obeyed this rule, neither Chargaff nor anyone else had the faintest idea why

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27 X-Ray Evidence In the early 1950s, a British scientist named Rosalind Franklin began to study DNA using a technique called X-ray diffractionIn the early 1950s, a British scientist named Rosalind Franklin began to study DNA using a technique called X-ray diffraction The X-shaped pattern in the image shows that the strands in DNA are twisted around each other like the coils of a spring, a shape known as a helixThe X-shaped pattern in the image shows that the strands in DNA are twisted around each other like the coils of a spring, a shape known as a helix

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29 The Double Helix The Double Helix At the same time Francis Crick, and James Watson, were trying to understand the structure of DNA by building three- dimensional models of the moleculeAt the same time Francis Crick, and James Watson, were trying to understand the structure of DNA by building three- dimensional models of the molecule In 1953, Watson was shown a copy of Franklin’s X-ray pattern. In his book The Double Helix, Watson wrote: “The instant I saw the picture my mouth fell open and my pulse began to race.”In 1953, Watson was shown a copy of Franklin’s X-ray pattern. In his book The Double Helix, Watson wrote: “The instant I saw the picture my mouth fell open and my pulse began to race.”

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32 Watson and Crick’s Conclusion: -DNA is a double helix in which two strands are wound around each other. -Each strand is made up of a chain of nucleotides. -The two strands are held together by hydrogen bonds between adenine and thymine and between guanine and cytosine.

33 Structure of DNA

34 Learning Targets for Section 12.2 Summarize the events that happen in DNA replicationSummarize the events that happen in DNA replication Relate the DNA molecule to chromosome structure.Relate the DNA molecule to chromosome structure.

35 12–2 Chromosomes and DNA Replication DNA and Chromosomes Most prokaryotes have a single circular DNA molecule that contains nearly all of the cell’s genetic information

36 Chromosome E. coli bacterium Bases on the chromosome Prokaryotic Chromosome Structure Section 12-2 Go to Section:

37 Differences between Prokaryotes and Eukaryotes Eukaryotic DNA is a bit more complicated. Many eukaryotes have as much as 1000 times the amount of DNA as prokaryotesEukaryotic DNA is a bit more complicated. Many eukaryotes have as much as 1000 times the amount of DNA as prokaryotes DNA Length DNA molecules are surprisingly longDNA Length DNA molecules are surprisingly long The chromosome of the prokaryote E. coli, contains 4,639,221 base pairsThe chromosome of the prokaryote E. coli, contains 4,639,221 base pairs

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39 Length of DNA This means that the nucleus of a human cell contains more than 1 meter of DNAThis means that the nucleus of a human cell contains more than 1 meter of DNA How can so much DNA be packed into each and every cell in our body?How can so much DNA be packed into each and every cell in our body?

40 Chromosome Structure Chromosome Structure Eukaryotic chromosomes contain both DNA and protein, tightly packed together to form a substance called chromatinEukaryotic chromosomes contain both DNA and protein, tightly packed together to form a substance called chromatin Chromatin consists of DNA that is tightly coiled around proteins called histonesChromatin consists of DNA that is tightly coiled around proteins called histones

41 Chromosome Structure Chromosome Structure Together, the DNA and histone molecules form a beadlike structure called a nucleosomeTogether, the DNA and histone molecules form a beadlike structure called a nucleosome This allows the chromosomes to be very tightly coiled up in the nucleusThis allows the chromosomes to be very tightly coiled up in the nucleus

42 Figure Chromosome Structure of Eukaryotes Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2 Go to Section:

43 DNA Structure Activity

44 DNA Replication When Watson and Crick discovered the double helix structure of DNA, there was one more remarkable aspect that they recognized immediately.When Watson and Crick discovered the double helix structure of DNA, there was one more remarkable aspect that they recognized immediately. The structure explained how DNA could be copied, or replicatedThe structure explained how DNA could be copied, or replicated Each strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairingEach strand of the DNA double helix has all the information needed to reconstruct the other half by the mechanism of base pairing

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46 DNA Replication DNA Replication During DNA replication, the DNA molecule separates into two strandsDuring DNA replication, the DNA molecule separates into two strands Then produces two new complementary strands following the rules of base pairing.Then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template, or model, for the new strandEach strand of the double helix of DNA serves as a template, or model, for the new strand

47 Figure 12–11 DNA Replication Section 12-2 Go to Section: Growth Replication fork DNA polymerase New strand Original strand DNA polymerase Nitrogenous bases Replication fork Original strand New strand

48 DNA replication animation DNA Replication animation DNA Replication

49 How DNA Replicates Start with a double strand of DNAStart with a double strand of DNA DNA replication is carried out by a series of enzymes. which “unzip” a molecule of DNADNA replication is carried out by a series of enzymes. which “unzip” a molecule of DNA

50 A – T G – C A – T C – G T – A C – G I’ve deleted the sugar- phosphate backbone for easier drawings Hydrogen bonds How DNA Replicates

51 A – T A - T G – C G - C A – T A T C – G DNAC G T – A unzips T A C – G C G DNA Unzips

52 A – T G – C A T C G T A C G DNAP III moves along each strand adding a base pair at a time

53 A – T G – C A T T C G G T T A C CG DNAP III continues to moves along each strand adding a base pair at a time

54 A – T G – C A T A T C G C G T A TA C G CG

55 Finally get 2 new strands, exact copies ATAT ATAT GCGC GCGC ATAT ATAT CGCG TATA CGCG

56 STOP: Practice Replicate the following strand of DNA ATG GGA CCG TAT ACG GAGATG GGA CCG TAT ACG GAG TAC CCT GGC ATA TGC CTCTAC CCT GGC ATA TGC CTC

57 DNA and Enzymes DNA replication involves a host of enzymes and regulatory moleculesDNA replication involves a host of enzymes and regulatory molecules The principal enzyme involved in DNA replication is called DNA polymeraseThe principal enzyme involved in DNA replication is called DNA polymerase In addition to replication DNA polymerase also “proofreads” each new DNA strand, helping to maximize the odds that each molecule is a perfect copy of the original DNAIn addition to replication DNA polymerase also “proofreads” each new DNA strand, helping to maximize the odds that each molecule is a perfect copy of the original DNA

58 Learning Targets for Section 12.3 What are the three main types of RNA?What are the three main types of RNA? What is transcription?What is transcription? What is translation?What is translation?

59 12–3 RNA and Protein Synthesis 12–3 RNA and Protein Synthesis The double helix structure explains how DNA can be replicated but it does not explain how a gene worksThe double helix structure explains how DNA can be replicated but it does not explain how a gene works Genes are coded DNA instructions that control the production of proteinsGenes are coded DNA instructions that control the production of proteins

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61 RNA The first step is to copy part of the nucleotide sequence from DNA into RNA a process called transcriptionThe first step is to copy part of the nucleotide sequence from DNA into RNA a process called transcription RNA molecules then carry out the process of making proteins.RNA molecules then carry out the process of making proteins. RNA molecule is a working copy of a single gene.RNA molecule is a working copy of a single gene. Using RNA makes it possible for a single gene to produce hundreds or even thousands of RNA moleculesUsing RNA makes it possible for a single gene to produce hundreds or even thousands of RNA molecules

62 The Structure of RNA There are three main differences between RNA and DNA: 1.The sugar in RNA is ribose instead of deoxyribose 2.RNA is generally single-stranded 3.RNA contains uracil in place of thymine

63 Types of RNA There are three main types of RNA: messenger RNA, ribosomal RNA, and transfer RNA. There are three main types of RNA: messenger RNA, ribosomal RNA, and transfer RNA. 1.messenger RNA (mRNA) serves as “messengers” from DNA to the rest of the cell. 2.ribosomal RNA (rRNA) is the site where Proteins are assembled on ribosomes 3.transfer RNA (tRNA) transfers each amino acid to the ribosome during the construction of a protein.

64 Transcription During transcription, RNA polymerase binds to DNA and separates the DNA strands.During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNARNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA

65 RNA DNA RNA polymerase Figure 12–14 Transcription Section 12-3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) Go to Section:

66 Transcription movie Transcription

67 Practice Transcribing Remember A goes with T, C goes with G and Uracil takes the place of ThymineRemember A goes with T, C goes with G and Uracil takes the place of Thymine TAC GCA CCA TAT CCG ATTTAC GCA CCA TAT CCG ATT AUG CGU GGU AUA GGC UAAAUG CGU GGU AUA GGC UAA

68 Where to Begin? The enzyme will bind only to regions of DNA known as promoters, which have specific base sequences.The enzyme will bind only to regions of DNA known as promoters, which have specific base sequences. Promoters are signals in DNA that indicate to the enzyme where to bind to make RNAPromoters are signals in DNA that indicate to the enzyme where to bind to make RNA Similar signals in DNA cause transcription to stop when the new RNA molecule is completedSimilar signals in DNA cause transcription to stop when the new RNA molecule is completed

69 Editing RNA Many RNA molecules have sections, called introns, edited out of them before they become functional. Many RNA molecules have sections, called introns, edited out of them before they become functional. The remaining pieces, called exons, are spliced together. Then, a cap and tail are added to form the final RNA molecule.

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71 The Genetic Code The “language” of mRNA instructions is called the genetic code.The “language” of mRNA instructions is called the genetic code. RNA contains four different bases: A, U, C, and G.RNA contains four different bases: A, U, C, and G. In effect, the code is written in a language that has only four “letters.”In effect, the code is written in a language that has only four “letters.”

72 STOP THINK! What is the process of transcription making?What is the process of transcription making? Where does transcription take place?Where does transcription take place? What enzymes are used to complete transcription?What enzymes are used to complete transcription? Compare and Contrast DNA and RNA?Compare and Contrast DNA and RNA?

73 Genetic Code  The genetic code is read three letters at a time  Each three-letter “word” in mRNA is known as a codon  A codon consists of three consecutive nucleotides that specify a single amino acid that is to be added to the polypeptide

74 Genetic Code Because there are four different bases, there are 64 possible three-base codons (4 × 4 × 4 = 64).Because there are four different bases, there are 64 possible three-base codons (4 × 4 × 4 = 64). The codon, AUG, that can either specify methionine or serve as the initiation, or “start,” codon for protein synthesisThe codon, AUG, that can either specify methionine or serve as the initiation, or “start,” codon for protein synthesis There are three “stop” codons that do not code for any amino acidThere are three “stop” codons that do not code for any amino acid

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76 Translation During translation, the cell uses information from messenger RNA to produce proteinsDuring translation, the cell uses information from messenger RNA to produce proteins This process is known as translationThis process is known as translation

77 Translation Before translation can occur, messenger RNA must first be transcribed from DNA in the nucleus and released into the cytoplasmBefore translation can occur, messenger RNA must first be transcribed from DNA in the nucleus and released into the cytoplasm Translation begins when an mRNA molecule in the cytoplasm attaches to a ribosomeTranslation begins when an mRNA molecule in the cytoplasm attaches to a ribosome

78 Messenger RNA Messenger RNA is transcribed in the nucleus. Transfer RNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. mRNA Start codon Ribosome Methionine Phenylalanine tRNA Lysine Nucleus Figure 12–18 Translation Section 12-3 mRNA Go to Section:

79 Translation As each codon of the mRNA molecule moves through the ribosome, the proper amino acid is brought into the ribosome and attached to the growing polypeptide chainAs each codon of the mRNA molecule moves through the ribosome, the proper amino acid is brought into the ribosome and attached to the growing polypeptide chain That job is done by transfer RNAThat job is done by transfer RNA

80 The codon matches up with complementary bases on the tRNA to tell it which amino acid to bring inThe codon matches up with complementary bases on the tRNA to tell it which amino acid to bring in The three bases on the tRNA molecule, called the anticodon, are complementary to one of the mRNA codonsThe three bases on the tRNA molecule, called the anticodon, are complementary to one of the mRNA codons Translation

81 Translation The polypeptide chain continues to grow until the ribosome reaches a stop codon on the mRNA moleculeThe polypeptide chain continues to grow until the ribosome reaches a stop codon on the mRNA molecule At that point the protein is released to be modified in the Golgi apparatus or to be shipped out to perform its functionAt that point the protein is released to be modified in the Golgi apparatus or to be shipped out to perform its function

82 The Polypeptide “Assembly Line” The ribosome joins the two amino acids— methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. mRNA Ribosome Translation direction Lysine tRNA Ribosome Growing polypeptide chain mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. Figure 12–18 Translation (continued) Section 12-3 Go to Section:

83 Practice Translating original DNAATG CCC AGT TCA TAAoriginal DNAATG CCC AGT TCA TAA Compl DNA = ___ ___ ____ ___ ____ mRNA = ____ ___ ____ ____ ____ Amino acid ______________, _______________, _____________, ______________, _____________.Amino acid ______________, _______________, _____________, ______________, _____________.

84 Check these answers first original DNAATG CCC AGT TCA TAAoriginal DNAATG CCC AGT TCA TAA Compl DNA = TAC GGG TCA AGT ATTCompl DNA = TAC GGG TCA AGT ATT mRNA = AUG CCC AGU UCA UAAmRNA = AUG CCC AGU UCA UAA

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86 Amino Acid Answers Amino acid methionine, proline,methionine, proline, serine, serine, stopserine, serine, stop

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88 BELLRINGER 11/11/09 COMPARE/CONTRAST RNA TO DNA *** Include as much information about each that you can think of THEN DESCRIBE what happens during TRANSCRIPTION And DESCRIBE WHAT HAPPENS DURING TRANSLATION

89 12.4 Learning Targets Describe how gene mutations and chromosomal mutations occur Understand the difference between point mutations and frameshift mutations

90 What is a mutation and where can it occur? Inheritable change in genetic code * 99.9 % are harmful. Only 0.1% are helpful!! What is a chromosomal mutation? Changes in number or structure of chromosome When do chromosomal mutations occur? During Meiosis – A cell division that produces gametes Ways variations can arise

91 TYPES OF MUTATIONS What is a frameshift mutation? Change that shifts the genetic message through inserting or deleting a nucleotide What is a point mutation? Change at one point of a chromosome.

92 What is a deletion mutation? Loss of one or more genes What is a duplication mutation? One or more genes are copied twice What is an inversion mutation? Part of a chromosome gets turned the wrong way

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