Thursday, July 21, 2011

MtDNA Diversity of Ghana: a forensic and phylogeographic view

Fendt et al


West Africa is characterized by a migration history spanning more than 150,000 years. Climate changes but also political circumstances were responsible for several early but also recent population movements that shaped the West African mitochondrial landscape. The aim of the study was to establish a Ghanaian mtDNA dataset for forensic purposes and to investigate the diversity of the Ghanaian population sample with respect to surrounding populations. We sequenced full mitochondrial control regions of 193 Akan people from Ghana and excluded two apparently close maternally related individuals due to preceding kinship testing. The remaining dataset comprising 191 sequences was applied as etalon for quasi-median network analysis and was subsequently combined with 99 additional control region sequences from surrounding West African countries. All sequences were incorporated into the EMPOP database enriching the severely underrepresented African mtDNA pool. For phylogeographic considerations, the Ghanaian haplotypes were compared to those of 19 neighboring populations comprising a total number of 6198 HVS1 haplotypes. We found extensive genetic admixture between the Ghanaian lineages and those from adjacent populations diminishing with geographical distance. The extent of genetic admixture reflects the long but also recent history of migration waves within West Africa mainly caused by changing environmental conditions. Also, evidence for potential socio-economical influences such as trade routes is provided by the occurrence of U6b and U6d sequences found in Dubai but also in Tunisia leading to the African West Coast via Mauritania and Senegal but also via Niger, Nigeria to Cameroon.

Population comparisons

"Ghana sequences clustered together with those populations being geographically closest (Sierra Leone, Guinea Bissau, Mali, Niger, Nigeria, Burkina Faso) which could reflect recent maternal gene flow and admixture among those areas. Also, geographically more distant populations clustered together such as Tunisia, Morocco, Libyan Arab Jamahiriya and Egypt as well as Ethiopia and Kenya, but also Senegal and Mauritania."

The data suggests that West African women of the Niger and Volta River basins cluster together genetically.

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