A dissertation submitted to the Faculty of Health Sciences, University of the
Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree
of Master of Science in Medicine
Johannesburg, 2014 / Evolution and historical events over the past 300 000 years have contributed in shaping the
gene pool of sub-Saharan African populations. By examining patterns of Y chromosome
variation, through the screening of single nucleotide polymorphisms (SNPs) and short
tandem repeats (STRs), the present study aimed to characterise the phylogeography of
ancient African Y chromosome haplogroups found in populations across sub-Saharan
Africa, as well as understand the genetic affinities of these populations.
In order to screen the large number of the markers required, seven multiplex single base
extension assays were developed. These were used to refine the resolution of Y
chromosomes commonly found in Africa, but also included a few markers to delineate the
common non-African Y chromosome haplogroups, following a hierarchical screening
process. In total, 1667 males were screened, and these data were compiled together with
comparative published data.
The resultant SNP and STR dataset was used in illustrating, more specifically, the
phylogeographies of haplogroups A and B. The wide geographic distribution of
haplogroup A, together with its position at the root of the phylogeny and high diversity,
support an early diversification of the haplogroup into its subclades, which subsequently
spread across Africa. The distribution of major haplogroup B subclades, however, are
possibly due to post-glacial migrations in the case of haplogroup B-M112, and recent
population expansions, leading to the common presence of haplogroup B-M152 across
sub-Saharan Africa. The spread of haplogroup E, however, created the biggest impact on
African populations; with its expansion likely resulting in the diminished presence of many
of the subclades of haplogroups A and B.
The Y chromosome compositions of present sub-Saharan African populations are, thus, the
result of several diversification events, followed by migration, and mixing of population
groups, over the course of modern human existence.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/17506 |
| Date | 22 April 2015 |
| Creators | Naidoo, Thijessen |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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