Biology 1001A Lecture Notes - Gene Duplication, Provirus, Arthur Kornberg
4 Sep 2013
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Document Summary
Mutations are highly important to the evolutionary process. Most of the mistakes that occur are base-pair mismatches. Depends on ability of dna polymerases to back up and remove mistakes. Has to happen immediately after the nucleotide is added. Nucleotide cannot remain as it cannot form proper h-bonds & shape of helix is distorted. Overall error rate is low (1 mispair per 1mil nucleotides) Essential, as if it is altered to work less efficiently you get 1 mistake per 1000- 10000 nucleotides (experimentally proven in prokaryotes and eukaryotes) Errors that escape proofreading increase accuracy beyond 1 in a million errors. Another round of correction by dna repair mechanisms. Mispairs cannot form proper bonds/ hold the shape of the helix. Gap left by mismatch removal is filled w/ dna polymerase and completed by repair enzymes move alone double helix and remove mismatches. Dna ligase , sealing the continuous molecule same repair mechanisms can repair damage done to dna by chemicals and radiation.
