1. Chapter 10 Homologous Recombination 27 and 29 September, 2004

2. Overview • Homologous recombination relies on regions of nearly identical sequence. • The Holliday model of the mechanism of recombination involves recognition, strand invasion, branch migration, and resolution. • The Double-strand Break Repair model is similar, but involves two Holliday junctions. • Homologous recombination is mediated by protein enzymes. • RecA (Rad51p) pairs homologous regions and promotes strand exchange. • RecBCD (Rad 50/58/60p; MRXp) generates single strand for invasion. • RuvAB and RuvC (?) promote branch migration and resolution. • Homologous recombination is required for successful meiosis. • In meiosis, Spo11 generates DSB, MRXp extends the break, and Rad51 promotes strand invasion. • Some events, including mating-type switching in yeast and VDJ recombination involve regulated, specific recombination.

3. Holliday Junction Cleavage and Strand Invasion

4. Holliday Resolution

5. DSB Recombination

6. DNA Damage leads to DSB

7. RecBCD and Chi Sites

8. Chi Site Polarity

9. RecA-catalyzed Strand Exchange

10. RecA - DNA Structures

11. Polarity of Cooperative RecA Binding

12. Mechanism of RecA Strand Exchange

13. RuvAB and Branch Migration

14. RuvC Resolves Holliday Structures

15. Meiotic Recombination

16. Spo11p forms Double-stranded Breaks

17. Recombination Mechanism

18. Mating-Type Conversion

19. The mechanism of mating-type conversion involves replication to bring about gene conversion.

20. Genetic and Physical Maps

21. Gene Conversion by Mismatch Repair

22. Resolving Paired Holliday Structures