Biology 1001A Chapter Notes - Chapter 9&12: Drug Resistance, Chromosome, Reactive Oxygen Species
10 May 2016
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Read chapter 12. 4 and 9. 4 from textbook: mechanism of proofreading. Ability of dna polymerases to back up and remove mispaired nucleotides from dna strand by breaking the backbone instead of forming backbones which is normally does. When newly added nucleotide base is mismatched, the dna polymerase uses a built-in deoxyribonuclease to remove newly added incorrect nucleotide. Dna polymerase can only continue adding nucleotides to a chain if the most recently added base is correctly paired: mechanism of mismatch repair. Base-pair mismatches that persist after proofreading 0 another round of correction by dna repair mechanisms. Base-pair mismatches distort the structure of the dna helix providing recognition sites for enzymes catalyzing mismatch repair. Repair enzymes scan dna helix for distortions on newly synthesized chain. If encounter distortion, they remove a portion of the new chain, including mismatched nucleotides. Gap filled by dna polymerase, using template as guide. Repair completed by dna ligase: difference between insertion sequences, transposons, and retrotransposons.
