A forensic analysis of genetic variation in the Botswana population

Abstract

This thesis has been placed under a long term embargo. Forensic and population genetic parameters were investigated in the Botswana population using autosomal and Y-chromosome short tandem repeat markers. AmpFlSTR Profiler plus markers were used to investigate the genetic diversity and forensic parameters in 773 individuals from Botswana from the reference database of the Botswana Police. The levels of polymorphism found using the AmpFlSTR Profiler Plus markers showed that the nine loci that make up the AmpFlSTR Profiler Plus can differentiate individuals for forensic casework in the Botswana population. AmpFlSTR Identifiler autosomal STR markers were used to investigate the population structure according to ethno-linguistics and geography 990 individuals from Botswana that serve as a reference database for the Botswana Police. Using pairwise genetic distances (Fst), analysis of molecular variance (AMOVA), factorial correspondence analysis (FCA), and the unsupervised Bayesian clustering method found in STRUCTURE and the landscape genetics software TESS, ethno-linguistics were found to have a greater influence on population structure than geography. The patterns of population structure found using these markers highlight the need for regional reference databases that include both ethnolinguistic and geographic location information. These markers have important potential for bio-anthropological studies as well as for forensic applications. The 17 Y-chromosomal short tandem repeats found in AmpFlSTR Y-filer and a highly discriminatory Y-STR genotyping system (the Y-STR 10-plex developed in the Forensics DNA Laboratory at the University of the Western Cape) were analysed in 249 unrelated male individuals from Botswana. Rst, multi-dimensional scaling (MDS) and AMOVA were used to investigate population differentiation in Botswana. The discrimination capacity (DC) was found to be higher using the Y-STR 10-plex as compared to the 17 markers in the Y-filer genotyping system. No geographic regional or ethnic differentiation was observed between the Northern and Southern regions of Botswana using both marker systems. Regional and ethnic variation can be useful in forensic working hypotheses. Cluster analysis using the highly discriminatory Y-STR 10-plex haplotypes may provide information about ancestry and haplogroup information.