Biology 1001A Lecture Notes - Lecture 8: Dna Mismatch Repair, Transposable Element, Dna Ligase
19 Nov 2012
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Document Summary
Mutations in dna may change protein which may change function, which is important for the evolutionary process. Transposition: mechanism of proofreading and likely result of proofreading defects. If nucleotide is mismatch, dna polymerase cannot continue to add nucleotides. If the nucleotide is mismatched, dna polymerase reverses using built-in de- oxyribonuclease (3"-5" exonuclease) to remove the incorrect nucleotide then it keeps going. If proofreading defects there is still mismatch repair: mechanism of mismatch repair. Second round of correction after proofreading correct base pairs fit together and their dimensions separate the sugar- phosphate backbone chains at a constant distance. Mismatched pairs will be too big or too small and so cannot form the hydro- gen bonds and so distort the structure of the dna helix. Dna ligase then comes and seals the nucleotide chain into a continuous. Will get carried on in replicated copies. May alter the property of the protein encoded.
