GENET270 Study Guide - Final Guide: Holliday Junction, Reca, Nucleoprotein
Document Summary
They are sensitive because rec proteins are used in many repair systems (sos response, recombination repair, etc. ), and uvr proteins are needed for nucleotide excision repair. A uvr2b complex binds anywhere on a dna strand, and moves along the strand until to encounters some type of damage. Uvrb binds the lesion, while uvr a is replaced by uvrc. The binding of uvrc causes uvrb to cut the dna backbone about four nucleotides to the 3" of the lesion. Meanwhile uvrc cuts the dna about seven nucleotides to the 5" of the lesion. This freed segment of dna (containing the damaged) is removed by uvrd helicase, and dna pol i synthesizes new dna using the healthy strand as a template. This is a case where the replisome doesn"t repair damage, but instead bypasses it, leaving behind gapped ssdna next to the damaged dna. This mechanism occurs during replication, and is a method of dna damage toleration, not repair.