The primary advantage of DS over other approaches is its superior accuracy. In our original publication on DS19, we demonstrated the direct measurement of the mutation frequency for the M13 bacteriophage as 2.5 × 10−6 mutations per base pair. We have subsequently measured mutation frequencies as low as 5 × 10−8 in human nuclear DNA (E.J.F. and L.A.L., unpublished results). In addition, we recently applied DS to measuring the mutation frequency of human mtDNA in brain tissue from young and old individuals33. We showed that the frequency of mtDNA point mutations is 10–100-fold lower than that previously reported, and the frequency increases approximately fivefold over an 80-year lifespan. Surprisingly, we observed no significant age-associated increase in the mutations most commonly associated with oxidative damage to mtDNA. This finding is inconsistent with free-radical theories of aging and suggests that previous studies indicating that reactive oxygen species induced mutations increase with age may be the result of PCR artifacts.
