CHAPTER 11 DNA and Its Role in Heredity

1. CHAPTER 11DNA and Its Role in Heredity

2. Chapter 11: DNA and Its Role in Heredity DNA: The Genetic Material The Structure of DNA DNA Replication The Mechanism of DNA Replication DNA Proofreading and Repair Practical Applications of DNA Replication

3. DNA: The Genetic Material • In addition to circumstantial evidence, two experiments demonstrated that DNA is the genetic material. 3

4. DNA: The Genetic Material • In one, virulent strain pneumococcus bacteria DNA genetically transformed nonvirulent bacteria into virulent bacteria. Review Figure 11.1 4

5. figure 11-01.jpg Figure 11.1 Figure 11.1

6. DNA: The Genetic Material • In a second, labeled viruses were incubated with host bacteria. • Labeled viral DNA entered host cells, producing hundreds of label-bearing viruses. Review Figures 11.2 and 11.3 6

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10. The Structure of DNA • X-ray crystallography showed that the DNA molecule is a helix. Review Figure 11.4 10

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12. The Structure of DNA • DNA is composed of nucleotides, each containing adenine, cytosine, thymine, or guanine. • There are equal amounts of adenine and thymine and equal amounts of guanine and cytosine. Review Figure 11.5 12

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14. The Structure of DNA • Watson and Crick proposed that DNA is a double-stranded helix with antiparallel strands, and with bases linked by hydrogen bonding. • Their model accounts for genetic information, mutation, and replication functions of DNA. Review Figures 11.6 and 11.7 14

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18. DNA Replication • Semiconservative, conservative, and dispersive models for DNA replication were hypothesized. Review Figure 11.8 18

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20. DNA Replication • Meselson and Stahl’s experiment proved replication of DNA to be semiconservative. • A parent strand is a template for synthesis of a new strand. • Two replicated DNA helices contain one parent strand and one synthesized strand each. Review Figures 11.9 and 11.10 20

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23. The Mechanism of DNA Replication • DNA polymerase catalyzes nucleotides to the 3’ end. • Nucleotides are added by complementary base pairing with the template strand. • The substrates, deoxyribonucleoside triphosphates, are hydrolyzed as added, releasing energy for DNA synthesis. Review Figure 11.11 23

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25. The Mechanism of DNA Replication • The DNA replication complex is in a fixed location and DNA is threaded through it for replication. Review Figure 11.12 25

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27. The Mechanism of DNA Replication • Many proteins assist in DNA replication. • DNA helicases unwind the double helix, the template strands are stabilized by other proteins. 27

28. The Mechanism of DNA Replication • Prokaryotes have a single origin of replication; eukaryotes have many. Replication for each proceeds in both directions from an origin of replication. Review Figure 11.13 28

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30. The Mechanism of DNA Replication • An RNA primase catalyzes the synthesis of short RNA primers, and to which nucleotides are added. Review Figure 11.15 30

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32. The Mechanism of DNA Replication • DNA polymerase action causes the leading strand to grow in the 5’-to-3’ direction until replication of that section of DNA is complete. • RNA primer is degraded and DNA replaces it. 32

33. The Mechanism of DNA Replication • On the lagging strand, growing in the other direction, DNA is made in the 5’-to-3’ direction but synthesis is discontinuous: • DNA is added as short fragments to primers, then the polymerase skips past the 5’ end to make the next fragment. Review Figures 11.16, 11.17 and 11.18 33

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37. DNA Proofreading and Repair • There is about one error in 106 nucleotide bases added in DNA replication, repaired by: proofreading, mismatch repair, and excision repair. • DNA repair mechanisms lower the error rate to about one base in 109. Review Figure 11.19 37

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39. DNA Proofreading and Repair • Although energetically costly and somewhat redundant, DNA repair is crucial to the survival of the cell. 39

40. Practical Applications of DNA Replication • The principles of DNA replication can be used to determine the nucleotide sequence of DNA. Review Figure 11.20 40

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43. Practical Applications of DNA Replication • The polymerase chain reaction technique uses DNA polymerases to repeatedly replicate DNA in the test tube. Review Figure 11.21 43

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