Development of a single base extension method to resolve Y chromosome haplogroups in sub-Saharan African populations

Abstract

Background: The ability of the Y chromosome to retain a record of its evolution has seen it become an essential tool of molecular anthropology. In the last few years, however, it has also found use in forensic genetics, providing information on the geographic origin of individuals. This has been aided by the development of efficient screening methods and an increased knowledge of geographic distribution. In this study, we describe the development of single base extension assays used to resolve 61 Y chromosome haplogroups, mainly within haplogroups A, B and E, found in Africa.

Results: Seven multiplex assays, which incorporated 60 Y chromosome markers, were developed. These resolved Y chromosomes to 61 terminal branches of the major African haplogroups A, B and E, while also including a few Eurasian haplogroups found occasionally in African males. Following its validation, the assays were used to screen 683 individuals from Southern Africa, including south eastern Bantu speakers (BAN), Khoe-San (KS) and South African Whites (SAW). Of the 61 haplogroups that the assays collectively resolved, 26 were found in the 683 samples. While haplogroup sharing was common between the BAN and KS, the frequencies of these haplogroups varied appreciably. Both groups showed low levels of assimilation of Eurasian haplogroups and only two individuals in the SAW clearly had Y chromosomes of African ancestry.

Conclusions: The use of these single base extension assays in screening increased haplogroup resolution and sampling throughput, while saving time and DNA. Their use, together with the screening of short tandem repeat markers would considerably improve resolution, thus refining the geographic ancestry of individuals.

Figure 1

Electropherogram and phylogeny of (a) YSNP1, (b) Hg-A, (c) Hg-B, (d) Hg-B2b, (e) Hg-E, (f) Hg-E1b1a, and (g) Hg-E1b1b1. The markers shown in parentheses are there to indicate the hierarchical nature of the phylogenies, and are not a part of the panels they are shown with.

Figure 2

Clustered column graphs of haplogroup frequencies in south eastern Bantu-speakers (BAN), Khoe-San (KS) and South African Whites (SAW).