Dissertation Research: Apportionment of African Genetic Diversity Based on Mitochondrial DNA, Y Chromosome, and X Chromosome Data

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Paleontological, archaeological, and genetic data all point to Africa as the continent where anatomically modern humans originated. However, it is still not known whether modern humans evolved in a small, isolated deme, or over a broader geographic area encompassing many African populations. While detailed analyses of the structure of African genetic variation should help to answer this question, there are very few studies at the nucleotide level other than those involving mtDNA. Here we propose to obtain DNA sequence data from multiple loci to characterize patterns of African genetic variability and to assess the degree of subdivision among modern African populations. The general research design is to examine DNA sequence variation at four unlinked, neutrally evolving loci in five African populations (n =200): the Khoisan, Southeast Bantu, Bakola, Dogon, and Dinka. Sequence data from the mitochondrial DNA, the Y chromosome, and two genes on the X chromosome will be compared. By examining four loci for which the reconstruction of gene trees is possible, we will be in a position to infer the time to the most recent common ancestor and mutational ages throughout the tree diagrams, and the degree (and age) of population structure at different times in human evolution. The proposed research will provide the first nucleotide-level estimate of African population subdivision based on multiple loci, and should lead to deeper insights into the effective population sizes of ancestral populations and the evolutionary processes that were involved during the transition to anatomically modern human form. The proposed project would involve the training of undergraduate and graduate students, as well as a member of the Sudanese refugee community in Tucson. Finally, this research will help to expand public knowledge of African population history and indirectly benefit populations that are underrepresented in current medical research.