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

古生物学、考古学和遗传学数据都指出非洲是解剖学上现代人类起源的大陆。然而，我们仍然不知道现代人类是在一个小的、孤立的群落中进化的，还是在一个包括许多非洲人口的更广泛的地理区域中进化的。虽然对非洲遗传变异结构的详细分析应该有助于回答这个问题，但是除了涉及mtDNA的研究之外，在核苷酸水平上的研究很少。在这里，我们建议从多个位点获取DNA序列数据，以表征非洲遗传变异的模式，并评估现代非洲人群的细分程度。总体研究设计是在5个非洲人群（n =200）中检测4个未连接的中性进化位点的DNA序列变异：科伊桑人、东南班图人、巴科拉人、多贡人和丁卡人。将比较来自线粒体DNA、Y染色体和X染色体上的两个基因的序列数据。通过检查四个基因座，我们可以重建基因树，我们将能够推断出最近的共同祖先的时间和整个树形图的突变年龄，以及人类进化中不同时期群体结构的程度（和年龄）。拟议的研究将提供基于多个基因座的非洲人口细分的第一个核苷酸水平估计，并应导致更深入地了解祖先人口的有效人口规模以及在向解剖学上的现代人类形态过渡期间所涉及的进化过程。拟议的项目将包括培训本科生和研究生，以及图森苏丹难民社区的一名成员。最后，这项研究将有助于扩大公众对非洲人口历史的了解，并间接使目前医学研究中代表性不足的人口受益。

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.