BICD 100 Lecture Notes - Lecture 5: Dna Repair, Dna Mismatch Repair, Dna Ligase
19 Dec 2016
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Acted on more harshly by natural selection than duplications (but, this is context dependent) (cid:449)illia(cid:373)"s s(cid:455)(cid:374)d(cid:396)o(cid:373)e lack of social inhibition: duplication. Often the fuel for the evolution of new genes. Strand breaks, put back together in wrong order: translocation. Strand breaks, parts are flipped between different chromosomes. Dna repair: proofreading, dna repair one strand damaged. Nucleotide excision repair: dna repair dsdna break (ds = double strand) What happens if an incorrect nucleotide is incorporated during replication: happens in 1 in ~10,000 nucleotides, most mistakes are caught, overall bacterial mutation rate is only 1 in ~ 1,000,000,000. Repli(cid:272)ati(cid:374)g dna pol(cid:455)(cid:373)e(cid:396)ases ha(cid:448)e 3" to 5" e(cid:454)o(cid:374)u(cid:272)leol(cid:455)ti(cid:272) p(cid:396)oof(cid:396)eadi(cid:374)g a(cid:272)ti(cid:448)it(cid:455: some dna polymerases can catch errors, cut it out, replace it with correct nucleotide. 3" to 5" e(cid:454)o(cid:374)u(cid:272)lease: recognizes incorrect nucleotide because of the change in shape. What about dna damage that arises independent of dna replication: estimated 10,000 to 1,000,000 mutational events per cell per day!
