Date of Award

1997

Degree Type

Thesis

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Science, Technology and Engineering

First Advisor

Prof Alan Bittles

Abstract

The purpose of the project was to assess the effects of inbreeding on the genetic constitution of two Pakistani bradaris (literally defined as brotherhoods). Both bradaris contain children born to consanguineous (first cousin) and nonconsanguineous marriages. DNA samples have been supplied by Dr Subaib Ahmed of the Armed Forces Institute of Pathology in Rawalpindi, for a total of 91 individuals. The specific allele frequencies, and levels of homozygosity of each bradari, were determined using twenty fluorescence-labelled microsatellite markers for chromosomes 13 and 15. Amplification of the DNA was performed using the polymerase chain reaction (PCR). The PCR products were separated electrophoretically on an ABI Prism 310 Genetic Analyzer, with GeneScan software employed to identify the alleles of each individual. Comparisons were made between the two bradaris, and between the bradaris and previously published data available from the GDB (Genome Data Base) and CEPH (Centre d'Etudes du Polymorphisme Hurnain). The level of homozygosity in each bradari was also compared to expected levels, calculated assuming random mating and with a correction for the inbreeding coefficient for each pedigree. The observed allele frequencies differed significantly between the bradaris for thirteen of the twenty markers. Allele frequencies in each bradari were also compared to the GDB and CEPH data and were found to be significantly different for all loci. The observed levels of homozygosity at each locus varied from 4% to 55% in the Khattar, and 3% to 40% in the Rajpoot. Observed homozygosity in each bradari was not statistically different from the GDB or CEPH data. Both the basic and corrected values for expected homozygosity were significantly greater than observed homozygosity in each bradari. An increase in homozygosity in the children of first cousin marriages was observed, however it was less than the predicted 6.25%. Lower than expected levels of homozygosity in the Pakistani families could indicate that there is preferential early selection against homozygotes in these families. There also appear to be reduced homozygosity levels in some regions of the two chromosomes, which may indicate that the resistance to homozygosity is specific to certain loci.

Included in

Genetics Commons

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