INTRA-POPULATION AND INTER-POPULATION DIVERSITY AT SHORT TANDEM REPEAT LOCI IN DIVERSE POPULATIONS OF THE WORLD

To study the level of intra- and inter-population variation at hypervariable DNA loci, we have characterized 15 human populations of diverse ethnic and geographic origins at six short tandem repeat loci by using the polymerase chain reaction. Even though the spectrum of allelic variation is quite broad and there are substantial differences in allele frequency distributions among populations, in general, populations within a major racial group show a greater degree of similarity. This observation is reflected in the analysis of gene diversity. When the total diversity is apportioned, the maximum variation becomes attributable to inter-individual differences within a population; of the variation that is attributable to differences between populations within a racial group and differences between racial groups, the former is smaller than the latter. Separate analysis of gene diversity for each of the major population groups based on geographic and ethnic relationship shows that the total gene diversity is higher for the larger racial groups, namely, African, Caucasian and Mongoloid, than the American Indians and the Pacific Islanders. As expected, a reciprocal relationship between gene diversity and F-ST levels is observed. Higher values of F-ST in the American Indian and the Pacific Islanders may reflect smaller population size and a higher level of isolation. An analysis of genetic distance encompassing the populations belonging to the three major racial groups recognizes three distinct clusters - all the populations of African affiliation cluster together, as do the Caucasian affiliated and the Mongoloid groups, in two distinct clusters. Interestingly, three broadly classified cosmopolitan US populations, namely, US White, US Black and US Asian, cluster with their ancestrally related populations. This study dispels some of the concerns regarding the applicability of DNA typing data for forensic use.