In addition to maternal inheritance, mtDNA and nDNA mutation rates differ. The low fidelity of mtDNA polymerase, the lack of protective histone proteins and a less effective repair system lead to a higher base substitution rate in mtDNA (Pinz and Bogenhagen, 1998). Within mtDNA, HV-I and HV-II appear to evolve quickly, with their mutation rates being about 5-10 times higher than that of nDNA (Budowle et al., 2003). Together with maternal inheritance, higher mutation rates have made mtDNA typing an interesting tool for human population genetics and evolutionary studies (Stoneking, 1994). Additionally, the somatic accumulation of mtDNA mutations has been proposed to play a role in human aging (Michikawa et al., 1999).
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