Mitochondrial DNA consensus sequence for the Tswana population of South Africa

Abstract

Evolutionary studies are critical in eliciting the fundamental phylogeny within and among populations of living organisms. Genetic diversity is displayed in human mitochondrial DNA (mtDNA) as haplogroups that consist of shared mutations, which are carried to the following generation through the maternal lineage. The current haplogroup hierarchies commonly used to describe and compare the genetic diversity of global human populations are based on the available mtDNA sequence variation datasets of numerous continent-specific populations. The description of mtDNA variation in human populations is furthermore of importance, as it allows the identification of population-specific genetic variation that has an effect on gene function, as well as on adaptation and susceptibility to disease. Owing to the limited amount of available mtDNA variation data from the numerous African populations currently residing in Africa, a lack of genetic diversity data exists for the determination of a sufficient baseline standard sequence representing the genetic variation present in African populations and thus also for a representative African haplogroup hierarchy. In this study, the mtDNA variation of 50 Tswana-speaking individuals from South Africa was determined and a novel Tswana consensus sequence was constructed to contribute to the urgent need for information of the mtDNA variation present in African populations. The consensus mtDNA sequence variation data obtained through this analysis should be regarded as a baseline for the observed sequence variance and genetic diversity of the maternal ancestral genetic pool of a Bantu-speaking population of South Africa. This study therefore contributes novel information regarding the mitochondrial genetic diversity of a South African Tswana-speaking population to the current body of literature. The results of this study provide strong evidence to support the ancient nature of African haplogroups and also provide evidence in support of the presence of Khoi-San maternal ancestry in the origins of the current Bantu-speaking populations of southern Africa. In addition, the observed sequence variation contributes to the current haplogroup hierarchy of African lineages and provides information in support of the previously reported distinct phylogenetic relationship between individuals of African and non-African origin, thereby explaining the high level of genetic diversity among and between African populations.