Browsing by Author "Rousseau, Jeanne"

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    HLA DRB1, DQA1, DQB1 and DPB1 polymorphisms in Namibian Khoi and San and in the Xhosa and South African mixed-ancestry population
    (2003) Rousseau, Jeanne; Williams, Jeanne; Creemers, Pauline
    We have analysed the HLA allele distributions in unrelated Namibian Khoi and San and South African Xhosa and mixed-ancestry (so-called Cape coloured) populations. The allelic specificities of the DRB1, DQA1, DQB1 and DPB1 loci were determined. We found loss of allelic diversity and predominance of certain alleles to be more pronounced in the San than in the Khoi. By contrast, the Xhosa indicated wide allelic diversity especially at the DRB1 and DPB1 loci. We found evidence that the Caucasoids may have been derived from an early migration wave, whereas African blacks arose from a later migration wave of an ancestral population pre-dating ethnic diversity. Frequencies in the Xhosa for the DRB10302, 1101, 1302 and 1304 alleles revealed clinal variation in a north-south direction across the African continent. For the DRB1, DQA1, DQB1 haplotypes there was greater variation in the Khoi than in the San, in whom certain haplotypes predominated. We found 13 previously unreported haplotypes. In Xhosa we found 30 different DRB1, DQA1, DQB1 haplotypes. Allele and haplotype characteristics and frequencies in the South African mixed-ancestry population were mostly intermediate between those found in Xhosa and reported for Caucasoids, and three possible ancestral southern African DRB1, DQB1, DPB1 haplotypes were found. We discuss the implications of our findings for organ donor transplantation in Xhosa and in the South African mixed-ancestry population.
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    The molecular basis of alpha thalassaemia in a South African population
    (1984) Rousseau, Jeanne; Rousseau, Jeanne; Mathew, Chris; Harley, Eric
    The molecular basis of alpha thalassaemia in the so-called 'Cape Coloured' population of the Western Cape was investigated. Restriction endonuclease digestion, Southern blotting and hybridisation with alpha and zeta globin-specific probes were used to investigate the incidence of the the various alpha thalassaemia determinants and their disorders. Results indicate that one determinant in this population results from the deletion of a single alpha globin gene on the short arm of chromosome 16. In individuals homozygous or heterozygous for this deletion, digestion with restriction endonuclease Bam H1 shows the presence of a shorter 10,5kb alpha globin-specific fragment as opposed to the 14kb fragment found in normal individuals. Individuals with both alpha globin genes deleted on the same chromosome i.e. the genotype --/aa, were detected and their alpha thalassaemia determinant characterised by: 1. a family study 2. quantification of the alpha/gamma glob in gene ratio, and 3. mapping with the zeta globin probe since the deletion extends into the zeta locus. The --/ alpha thalassaemia determinant was found to be of Southeast-Asian origin. A non-deletion form of alpha thalassaemia was also detected in which the alpha globin restriction map appeared to be normal. This condition may have resulted from a point mutation within the alpha ilobin gene region which affects transcription or RNA processing. The DNA of infants born with detectable levels of Hb Bart's in their cord blood was investigated in order to estimate the frequency of the single and double gene deletions in this population. The results indicate that infants with Hb Bart's in the 4 - 8% range predominantly have the genotype -a/-a. Using the data obtained the incidence of the heterozygote was calculated according to the Hardy-Weinberg equation. The calculated incidence of the heterozygote (-a/aa) was found to be 16,9%.