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Replication of the Genetic Material

Replication of the Genetic Material. Genetic material must be duplicated for transfer into daughter cells. Complementary double-stranded DNA makes this possible. A. A. A. Possible Mechanisms for DNA Replication. semiconservative conservative dispersive.

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Replication of the Genetic Material

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  1. Replication of the Genetic Material Genetic material must be duplicated for transfer into daughter cells. Complementary double-stranded DNA makes this possible A A A

  2. Possible Mechanisms for DNA Replication semiconservative conservative dispersive Which is correct?

  3. Meselson - Stahl Experiment (1958) Nitrogen isotopes Density gradient centrifugation - CsCl

  4. Meselson - Stahl Experiment Definitely not conservative Results also consistent with dispersive

  5. Meselson - Stahl Experiment Supports only semiconservative model

  6. Replication of DNA in Eukaryotic Chromosomes How is DNA arranged and replicated?

  7. Replication of DNA in Eukaryotic Chromosomes Taylor, Woods, and Hughes (1958) CHO harlequin chromosomes

  8. DNA Polymerase Chain Elongation Chain growth - 5’ to 3’ direction 3’ 5’ 5’ 3’ 8

  9. DNA Polymerase Chain Elongation 9

  10. Replication Origin Bidirectional Replication from Origin Single origin in Prokaryotes 10

  11. Replication Origins - Replicons Multiple origins in Eukaryotes Replicons 11

  12. Primer Requirement 12

  13. Initiation of DNA Replication - E. coli Initiator protein DnaA binds oriC denaturation DNA helicases unwind DNA DNA primase makes primers 13

  14. Replication Fork - Okazaki Fragments 5’ Initial primers Repriming Discontinuous synthesis Lagging strand Continuous synthesis Leading strand 3’ 5’ 3’ 5’ 3’ 5’ 3’ 14

  15. Activities of DNA Polymerases 15

  16. Types of DNA Polymerases E. Coli DNA polymerase I - single polypeptide DNA polymerase III - three polypeptide holoenzyme Both capable of chain growth and 3’-5’ exonuclease activity Only pol I has 5’ - 3’ exonuclease activity Eukaryotes > 15 polymerases, 3 involved in replication of nuclear DNA pol  - with primase, creates RNA/DNA primer pol  and pol  - extend primers on leading/lagging strand 16

  17. Joining of Okazaki Fragments 17

  18. DNA Replication in E. coli (Fig. 3.6) Initiation Elongation Primer Removal Ligation 18

  19. DNA Replication in E. coli Figure 3.8. Replisome Model. DNA pol III on lagging-strand template is finishing synthesis of an Okazaki fragment. 19

  20. Telomere Problem Due to: Linear chromosomes & Requirement for RNA primers 20

  21. Resolving the Telomere Problem 21

  22. Rolling Circle Replication 22

  23. Rolling Circle Replication in Phage  23

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