BCHM 4116 1st Edition Lecture 20 Outline of Last Lecture I Recombination Outline of Current Lecture I DNA Repair Current Lecture 1 DNA Repair a Human genome has 150 genes associated w DNA repair b DNA repair system includes i Direct reversal damage repair 1 Chem Rxn that reverse damage returning DNA to proper state ii Single strand damage repair 1 Relies on complementary strand to guide repair 2 Mismatch repair MMR a Mismatched during replication b Scans excises mismatched region replaces c KEY to tell which strand is newly synthesized and thus contains mismatch is via METHYLATION i Newly synthesized strands are not yet methylated whereas parent strand is d Endonuclease cuts new unmethylated strand exonuclease removes mismatched base DNA pol III holoenzyme fills gap w correct bases ligase reseals strand 3 Base excision a For single bases that have been damaged via oxidation or other chemical modification b DNA GLYCOSYLASE removes damaged base i Cleaves N glycosidic bond creates AP site c AP ENDONUCLEASE i Cleaves backbone removes deoxyribose P d DNA Pol i Repairs gap e DNA ligase i Reseals 4 Nucleotide excision a Repairs larger regions of damaged DNA than base b Cuts sugar phosphate backbone of DNA These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute c DNA Pol fills in gap d DNA ligase reseals
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