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Determination of Early Human Intercontinental Migration from Genomic IBD segment Flow

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2016, Master of Science in Biomedical Sciences (MSBS), University of Toledo, Biomedical Sciences (Bioinformatics and Proteomics/Genomics).
Previous research demonstrated that genomic Identity by Decent (IBD) segments are a means of revealing distant relatedness between individuals from the same or different continents. When these segments are identically shared in one or more loci between individuals from different continents the inference is that these individuals are distantly related. IBD segments are characterized by rare variant clusters (RVCs) of 5 or more very rare genetic variants (vrGVs) with minor allele frequencies >2%. Although RVCs are a means of detecting distant genetic relatedness they cannot determine the directional flow of these IBD segments between continents. My objective was to determine the directional flow of these IBD segments from continents to continent after generations of admixture and to infer human continental migratory history. To perform this task, I analyzed continental allelic frequency differences of SNPs located within IBD segments coordinates of related pairs of individuals’ genomic data. Also, the occurrence of these SNPs in homozygous and heterozygous forms between pairs of individuals when there was a statistically significant difference in the allele frequencies of these SNPs from continent to continent. This experiment comprised individuals from African and Asian populations which shared the least number of IBD segments and African and European populations. Between the African and Asian populations, there was a clear majority (85%) of IBD segments analyzed flowing from Africa to Asia versus 15% from Asia to Africa. As for the IBD segments shared between the African and European populations there was a less definite result with 57% of segments flowing from Africa to Europe and 43% in the opposite direction. Given that the median size of IBD segments found between Asian and African populations was the smallest (54kb) compared to other intercontinental population comparison, there can be a conclusion that the admixture between the African and Asian populations is the most ancient given that with every generational admixture, IBD segments reduce in size from further admixture. These results would tend to imply that there was an ancient migratory event of Africans to Asia with some back migration occurring from Asia to Africa. On the other hand, my data suggest an almost equal degree of migration between African and European populations with a little more migration from Africa to European as opposed to migration from Europe to Africa. With this method of analyzing IBD segment flow it is difficult to determine whether these migrations occurred hundreds of thousands of years ago or more recently because of external issues like recombination and mutation events which would affect IBD segments size. However, we get a general idea of migration patterns that have taken place between continents
Alexei Fedorov (Committee Chair)
102 p.

Recommended Citations

Citations

  • Mainsah, J. S. (2016). Determination of Early Human Intercontinental Migration from Genomic IBD segment Flow [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=mco1479319602398361

    APA Style (7th edition)

  • Mainsah, Joseph. Determination of Early Human Intercontinental Migration from Genomic IBD segment Flow. 2016. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=mco1479319602398361.

    MLA Style (8th edition)

  • Mainsah, Joseph. "Determination of Early Human Intercontinental Migration from Genomic IBD segment Flow." Master's thesis, University of Toledo, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=mco1479319602398361

    Chicago Manual of Style (17th edition)