Pusat Pengajian Sains Kesihatan - Tesis

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    Genetic profiling of five major Ghana population using Short Tandem Repeat and mitochondrial DNA sequences for forensic and ancestry study purposes
    (2022-11)
    Abban, Edward Kofi
    Population datasets of forensically relevant short tandem repeat (STR) and mitochondrial DNA (mtDNA) from a particular population group are needed before any DNA profile test results can be reliably submitted into evidence before the court. These population datasets are proven useful for calculating match probabilities in forensic or disputed paternity cases and for population genetic studies. However, autosomal and Y-chromosome STR and mtDNA sequence datasets for representative African populations, including Ghana, are lacking compared with European and Asian populations. Therefore, the present study is conducted to provide the first-ever STR and mtDNA population datasets that were screened from the same set of individuals representing the Akans, Ewe, Ga-Dangbe, Mole-Dagbon and Guang sub-populations in Ghana. Twenty-one autosomal STR loci in 515 genomic samples of these subpopulation groups were typed using Investigator 24plex PCR amplification kit. The match probability of identity ranged from 1 in 1.30x10-25 to 6.28x10-26, and the combined power of discrimination ranged from 0.9999999999468 to 0.9999999999864. Genetic distances, phylogenetic tree and principal coordinate analysis (PCoA) revealed that the five populations are genetically closer to each other and neighbouring populations than distant localities. Unrelated males (n=268) were then genetically characterized for 23 Y-chromosome STR loci using Powerplex Y23 STR kit. The haplotype diversity, discriminating capacity and match probability for the pooled population data were 0.9998, 0.9627 and 0.0039, respectively. The pairwise genetic distance (RST) for the Ghanaian datasets and other reference populations deposited in Y-STR Haplotype Reference Database were estimated and mapped using multidimensional scaling (MDS) plot. The Guan and Ewe were significantly different from the Akan, Mole-Dagbon and Ga-Dangme, but were all plotted closely with reference African populations in the MDS data mapping. The entire mtDNA control region in 207 unrelated individuals of the five major sub-populations of Ghana were obtained using Sanger sequencing method. Results showed an admixture of mtDNA types derived mainly from Africans (97.59%) and a minor proportion from Asians (0.48%) and Europeans (1.93%). A high value of genetic diversity (0.9994), power of discrimination (0.9991) and low value of random match probability (0.054) indicate that mtDNA analysis for this population can effectively be used for forensic casework. The most frequent mtDNA lineages were L (97.59%) and followed by U (1.45), N (0.48) and X (0.48), and Ghanaian sub-populations are closer to West African populations in PCoA data mapping. Overall, the present study has successfully typed and developed STR and mtDNA datasets for the five sub-population groups in Ghana. The statistical results showed that both markers are reliable for forensic DNA profiling purposes and for studying genetic makeup in Ghana. Future studies should focus on the other aspects of DNA profiling, such as validating newly DNA extraction and genotyping kits and developing population data (STR, mtDNA or other potentially relevant markers) for the remaining uncharacterized population groups in Ghana.