1. Microbial Genetics (Micr340) Lecture 14 DNA Repair and Mutagenesis

2. Definitions Lesion: chemical damage in DNA Mutagens: chemical compounds that cause lesions in DNA which can kill cells and can also increase frequency of mutations in DNA

3. Evidence for DNA repair

4. Specific Repair Pathways Repair of deaminated bases Damage due to reactive oxygen Alkylation of DNA and repair Pyrimidine dimer repair

5. Base Deamination by nitrous acid

6. Spontaneous Base Deamination

7. Repair of altered bases by DNA glycosylases

8. Damage due to reactive oxygen

9. Mechanism of avoiding GO

10. Alkylation Of guanine

11. Repair of alkylated DNA Specific N-glycosylases Methyltransferases

12. Pyrimidine Dimer Formation

13. Photoreactivation

14. General Repair Mechanisms Methyl-directed mismatch repair system Nucleotide excision repair SOS inducible repair

15. A model for methyl Directed mismatch repair

16. A model for nucleotide excision repair

17. SOS response

19. Regulation of SOS mutagenesis in E. coli