3. Electronic Theses and Dissertations (ETDs) - All submissions

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    Blood group polymorphisms in Southern Africa and innate resistance to plasmodium falciparum
    (1992) Field, Stephen Paul
    The observation by Haldane in 1949 that the distribution of malaria and certain thalassaemias were similar and that the former disease must be a selective force tor the continued existence of the latter by preservation of the heterozygotes. This theory which later became known as lithe malaria hypothesis" has been applied to other inherited conditions such as G6PD deficiency, membranopathies, certain blood group polymorphisms, other heamoglobinopathies such as sickle cell disease, blood group polymorphisms and more recently HLA phenotypes. It has been shown that the Duffy blood group antigens are the receptors for. Plasmodium vivax and since these antigens are lacking in most black Africans this species of malaria is virtually absent in Africa. It has also been shown that the glycophorins are at least in part the receptors for Pfalciparum. Several variants of the glycophorins exist and the biochemistry and, where known, the molecular mechanisms by which these arise is reviewed. Experimental work is carried out to establish the growth characteristics of Pfalciparum in an in vitro culture system using cells with glycophorin variants on their membranes. Three such variants were compared to normal cells and two (S~s-U-and Dantu) were found to be partially resistant to invasion by Pfalciparum merozoites whereas the third (Henshaw) was found to be no different to controls.
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    Mitochondrial DNA polymorphisms in Southern African populations.
    (1993) Soodyall, Himladevi
    The subject of this thesis is mitochondrial DNA (mtDNA) variation in southern African populations. The purpose of this study was twofold. Firstly, mtDNA variations were used to investigate the genetic affinities of Negroid, Khoisan, Caucasoid and "Coloured" populations in an attempt to refine theories on southern African population affinities and prehistory. MtDNA variations were detected using two different methods. The first method makes use of restriction fragment length polymorphisms (RFLPs) detected with the restriction enzymes Hpal, BamUI, Haell, Mspl, Avail and Hindi in 795 unrelated individuals from twenty ethnic groups within the Khoisan, Negroid, Caucasoid and "Coloured" populations from South Africa and Namibia. The combinations of the various restriction enzyme patterns (morphs) for the enzymes Hpal, Bam HI, Hae II, Mspl, Avail and Hindi (in this order), were used to derive the mtDNA type for each individual studied. This resulted in the discovery of 52 distinct mtDNA types: 30 of which had been previously reported, 28 out of 32 resulted from new combinations of enzyme morphs and 4/32 were due to the discovery of new enzyme morphs (MspI-17 in the Ashkenazi Jewish population and AvaII-31, AvaII-32 and AvaII-33 in the South African "Coloured" population). The second method involves sequencing approximately 750 base pairs of mtDNA contained within the two hypervariable segments within the non-coding control region of the mtDNA molecule in 144 individuals, most of whom where investigated for mtDNA RFLP variations. Pairwise comparisons of mtDNA sequences revealed 119 variant sites which gave rise to 129 unique mtDNA types.
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    Y-specific restriction fragment length polymorphisms In Southern African populations.
    (1992) Spurdle, Amanda B
    Seven Y chromosome probes and thirteen restriction enzyme digests were used to examine a conservative estimate of 20000bp, and no new Y-specific polymorphisms were revealed by these systems. The Y chromosome probe 49a, which reveals a Y-specific haplotype with TaqI, was shown to reveal five new complex polymorphisms with Bglll, Hindlll, Pst I, PvuII and Sstl. The new polymorphisms exhibit great genetic diversity, and each enzyme reveals numerous haplotypes, which mostly occur infrequently and are population-specific. The haplotypes for a given enzyme do not correlate strictly with those revealed by the other enzymes, including TaqI, suggesting that each polymorphism results from a combination of restriction site mutations and rearrangement events. Association between the different 49a polymorphisms occurs only in individuals of recent common genetic origin. Y-specific 49a/TagI haplotypes were determined for 933 individuals drawn from 23 different African populations. A total of 31 new haplotypes were observed, some of which contained new alleles or allelic variants. Duplication, in addition to CpG mutation, is implicated in the generation of certain allelic variants. Cluster analysis of genetic distances between populations was calculated using the 49a/TagI haplotype frequencies. Y-specific 49a/TagI haplotype analysis of individual populations was not sufficiently sensitive to accurately distinguish between the different Bantu-speaking Negroid tribal groups. Cluster analysis of larger groupings was more stable, and with the exception of the Khoisan, resulted in a basic split between African and non-African populations. The linkage disequilibrium of the XY275 MspI Y-linked polymorphism was determined. The high allele was generally found in association with the Y chromosome, but the Y-associated low allele was found to occur in Bantu-speaking Negroids, Khoisan-speaking Negroids, the Khoisan, two groups of mixed ancestry, and the Caucasoid South African Asiatic Indian population. The discovery of Y-associated low alleles in non-African as well as African populations suggests that more than one Y chromosome gave rise to the present-day non-African population. The pDP31/EcoRI, p21Al/TagI and Y Alu polymorphisms were also studied in several southern African populations. The pDP31 duplication occurred at high frequencies in Caucasoids, and could be used to indicate Caucasoid male gene flow into hybrid populations. The p21Al/TagI point mutation showed no distinct trends in frequency in the different populations, and several Taql mutations are proposed to have occurred in the repeat unit recognized by this sequence. The Y Alu polymorphism occurred infrequently in Caucasoids, at intermediate frequency in the Khoisan, and at high frequency in Negroids. The presence of the Y Alu insertion in all three major population groups studied is interpreted to suggest that the insert predates the diversification of Homo sapiens. The relationship between the different Y-linked polymorphisms was determined in the populations studied. The Y Alu polymorphism is believed to have originated once from sequencing data, but such information is not available for the other Y polymorphisms studied. No absolute relationship was observed between the Y Alu polymorphism and the 49a/TagI, XY275 Mspl, pDP31/£coRI and p21Al/TagI polymorphisms. It is suggested that the latter polymorphisms have arisen more than once.
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    Variable number of tandem repeat polymorphisms of man in Southern Africa.
    (1992) Marques, Isabel Maria
    Two classes of hypervariable loci, VNTRs and (CA)n repeats, represent a rich source of highly polymorphic markers in the human genome. The main objective of this study was to assess their usefulness in elucidating the relationships between 17 southern African populations and to assess the feasibility of paternity testing using these hypervariable markers in the local context.
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