As I was reading through the GENEALOGY-DNA list from Rootsweb this morning, I came across a great question about the frequency of mutation of mitochondrial DNA (mtDNA).
The listmember asks “I am wondering if anyone would know the odds of having a mutation between my brother and me in our mtDNA. Marker 16163 is G for one of us and A for the other…” This is a great question, and one that I’ve been asked as well.
In response, Ann Turner writes “The mutation rate hasn’t been studied in the detail I’d like to see. The largest study for the hypervariable regions was based on deep-rooting pedigrees from Iceland. They found 3 mutations out of 705 transmission events.”
The study, available here (pdf, HT: Ann Turner) was conducted through deCODE Genetics and Oxford University. They used 26 Icelandic ancestral trees to identify maternally-related individuals, and sequenced 272 mtDNA control regions representing a total of 705 transmission events. The researchers found a total of three mutations, resulting in a mutation rate of 0.0043 per generation, or 0.32/site/1 million years. A previous study (Parsons et al., 15 Nature Genetics 363 1997) found a total of 10 mutations in 327 transmission events for a frequency of 2.5/site/1 million years, and yet another study found 2 mutations in 81 transmissions for a rate of 0.75/site/1 million years (Howell et al., 59 Am J Hum Genet 501). The huge differences in these numbers suggests that much more research needs to be done, probably with a much larger dataset. If I had unlimited funds, I would also be interested to see if there are different mutation rates among haplogroups, as well as a number of other factors.