Mutation rates

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  • The most common source of mutation is due to mistakes made during DNA replication when an incorrect nucleotide is incorporated into newly synthesised DNA.
  • The mutation rate due to errors made by the DNA polymerase III replisome is one error for every one hundred million bases (nucleotides) that are incorporated into DNA, i.e. 1e-8
  • Technically, these aren't mutations; they count as DNA damage until the problem with mismatched bases in the double-stranded DNA has been resolved.
  • The DNA repair mechanism fixes 99% of this damage but 1% escapes repair and becomes a mutation. The error rate of repair is 10e-2 so the overall error rate during DNA replication is 10e-10 nucleotides per replication.
  • One error will occur for every 10 billion nucleotides (10e-10) that are incorporated into DNA
  • The rate of fixation of neutral mutations is equal to the mutation rate so by measuring the accumulation of neutral mutations in various lineages of bacteria you can estimate the mutation rate provided you know the time of divergence and the generation time.
  • The mutation rate in eukaryotes should be about the same since the properties of the DNA replication machinery are similar to those in eukaryotes. Measured values of mutation rates in yeast, Caenorhabditis elegans, Drosophila melanogaster, mouse and humans are all close to 10e-10