1. Replication

2. Central Dogma of Information Flow

3. Wagging the Dogma

4. Replication- the synthesis of DNA using itself as a template. Three stages: Initiation, Elongation, Termination Replication

5. Meselson-Stahl Experiment Replication is Semiconservative

6. Initiation

7. Origin of replication (ori) Replication Begins at a Specific Place Each Time

8. Theta structure Replication is Bidirectional

9. Helicase ssb DNA Must be Uncoiled Before Replication

10. Replication is 5’ -> 3’

11. Okazaki Fragments are Used to Synthesize the Lagging Strand

12. Primase Primers are Needed for Synthesis

13. Elongation Reaction

14. Termination Least well understood

15. Review of Replication - Initiation Ori bound by helicase and SSB (other proteins at site) Replication bubble forms primase and DNA polymerase III join complex Okazaki fragments used on lagging strand synthesis is 5’ to 3’

16. Review of Replication - Elongation PPi product polymerase I removes RNA and fills gap

17. Review of Replication - Termination Ligase seals nick (ATP dependent) Topoisomerase supercoils DNA (cut, wrap, ligate)

18. Proofreading 1 mistake every 10 5 - 10 6 bases during replication (3’ -> 5’ exonuclease activity) In DNA, 1 mistake every 10 8 - 10 9 bases other repair mech. must exist

19. Repair Mechanisms Mismatch repair Base Excision repair Nucleotide Excision Direct Repair

20. In Eukaryotes, the Major Differences are the Numbers and Names of the Molecules Prokaryotes Eukaryotes 1 ori and termultiple ori and ter Polymerases III and I Pol’s  and  Okazaki fragments ~1000 ~100-250 nt supercoiling histones