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

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Microbial Genetics (Micr340) Lecture 14 DNA 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

Alkylation Of guanine

Repair of alkylated DNA Specific N-glycosylases Methyltransferases

Pyrimidine Dimer 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

Regulation of SOS mutagenesis in E. coli