lacZ mutant frequencies for products of pol gap filling.
Purified human POLG with or without the proofreading exonuclease domain (Exo+ or Exo-, respectively) was incubated with a DNA sequence containing a gap in the lacZ gene in the presence of either equal ratios of dNTPs or tissue-specific mitochondrial ratios of dNTPs. As expected, the mutation frequency was higher in Exo- than Exo+ across all ratios due to the loss of proofreading activity. The data show that the frequency of mutation is higher for dNTP pools like those in mitochondria than in dNTP pools with equal ratios.(ND = not determined.)
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Did you know that you have a second genome? Small cellular organelles called mitochondria contain their own circular DNA. What happens to your cells when this DNA mutates?
