Microbial Genetics (Micr340)

Lecture 14DNA Repair and Mutagenesis

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

Evidence for DNA repair

Specific Repair Pathways

Repair of deaminated bases Damage due to reactive oxygen Alkylation of DNA and repair Pyrimidine dimer repair

Base Deamination by nitrous acid

Spontaneous Base Deamination

Repair of altered bases by DNA glycosylases

Damage due to reactive oxygen

Mechanism of avoiding GO

AlkylationOf guanine

Repair of alkylated DNA

Specific N-glycosylases Methyltransferases

PyrimidineDimer Formation

Photoreactivation

General Repair Mechanisms

Methyl-directed mismatch repair system

Nucleotide excision repair SOS inducible repair

A model for methyl

Directed mismatch

repair

A model for nucleotide excision repair

SOS response

SOS response

Regulation of SOS mutagenesis in E. coli