BIO 350 Lecture Notes - Lecture 8: Dna Mismatch Repair, Dna Repair, High Fidelity

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27 Feb 2019
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What is meant by dna damage: dna damage can be divided into two major classes, distorting, distorts dna helix structure, may inhibit replication and/or transcription, nicks, or breaks in dna, addition of a chemical adduct. Inappropriate covalent linkage (e. g. thymine-thymine dimer: non-distorting, minor structural consequences, replication is uninhibited, transcription may proceed (gene product may or may not be functional, single base change (transition or transversion) High fidelity dna repair: direct removal and replacement of damaged dna. What other mechanism can restore sequence: damaged dna is replaced using recombination-repair a mode of filling a gap in one strand of duplex dna by retrieving a homologous single strand from another duplex. Repair systems correct non-distorting dna damage: repair systems recognize incorrect base pairing. Excision systems remove and replace bases from one strand of dna at the site of damage: deamination of cytosine creates a u-g base pair.