Biology 1002B Study Guide - Midterm Guide: Copy-Number Variation, Cell Nucleus, Indel
30 Jan 2018
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Document Summary
Depends on the ability of dna polymerase to back up and remove mispaired nucleotides from a dnaa strand. The correct base pairs allow the fully stabilizing hydrogen bonds to form. If a newly added nucleotide is mismatched, the dna polymerase reverses using a built in 3"-5" deoxy-ribonuclease (exonuclease) to remove the newly added incorrect nucleotide. The enzyme resumes working forward, extending the new chain in the. 3"-5" by inserting the correct nucleotide: mechanism of mismatch repair: Any base-pair mismatches that remain after proof-reading face still another round of correction by this mechanism. The base mismatches distort the structure of the dna helix. These distortions provide a recognition site for the enzymes catalyzing mismatch repair. The repair enzymes move along the dna scanning for distortions. If the enzymes encounter a distortion, they remove a portion of the new chain, including the mismatched nucleotides.
