1Anthropology, University of South Florida, 2Dipartimento di Biologia ed Evoluzione, Università di Ferrara, 3Dipartimento di Biologia evoluzionistica sperimentale, Università di Bologna., 4Investigaciones, Academia Costarricense de Ciencias Genealógicas, 5Escuela de Biología, Universidad de Costa Rica
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A reliable estimate of the mutation rate of human mtDNA is of outmost importance in evolutionary studies of human population divergence and macroevolution. Yet the estimates obtained in phylogenetic and pedigree-based studies differ, with the former reporting lower and the latter reporting higher mutation rates.
The purpose of this paper was to determine the mtDNA mutation rate in a pedigree-based study. The data consist of maternal genealogies started from 152 living subjects. We only considered 19 genealogies, which included more than one living descendant, to determine if a mutation had occurred which differentiated the living subjects. Methods used for mtDNA extraction and analysis of the HVRI are in Castri et al., (2009).
We excluded two pedigrees whose living descendants had numerous HVRI differences, indicating that an ancestor was adopted. One of the mutations we observed (at site 335) is reported by Bandelt et al. (2000) as a “speedy site”. By eliminating the pedigree with this mutation, we have three mutations in 237 meiotic events with a mean maternal age of 28.3 years. If we use a generation time of 28.3 years we observe a mutation rate of 0.0126, which yields the following estimates: 35.16 x 10-6 substitutions per site per generation, 1.24 x 10-6 substitutions per site per year and a divergence rate of 2.48 x 10-6 substitutions per site per year.
Our study supports previous proposals that the mtDNA clock ticks faster when observed at the minute detailed level of human generations.
This project was supported by a grant from the National Institutes of Aging (1-R03-AG022616-01) to LM and by Italian MIUR Grants to DP and DL.