bme 130 – genomes lecture 23 genome evolution i: mutations, repair, and recombination
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BME 130 – Genomes
Lecture 23
Genome evolution I:
Mutations, repair, and recombination
TransitionsA GC T
TransversionsA CA TC GT G
When and how do mutations
happen?
DNA polymerases are not perfect:DNA polIII error rate =~ 1 x 10-7
Minimizing polymerase error
Polymerase slippage leads to indels
Slippage can get progressively worse
Mutagens and other -agens
Chemical mutagens
Figure 16.6a Genomes 3 (© Garland Science 2007)
(nitrous acid)
Physicalmutagens
UV radiation
Abasic site
Consequences of mutations
Mutations in gene sequence
Figure 16.12 Genomes 3 (© Garland Science 2007)
Figure 16.13 Genomes 3 (© Garland Science 2007)
Figure 16.14 Genomes 3 (© Garland Science 2007)
DNA repair
Minor pathway
Recognizes distortion of DNA
double helix
Similar concept for eukaryotes;
TFIIH helicase is used;
transcription coupled repair
Base mismatch: who is right?
DNA break repair
SOS!(why only in bacteria?)
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