POPULATION-GENETICS OF SHORT TANDEM REPEAT (STR) LOCI

To investigate the population genetics of short tandem repeat (STR) po lymorphisms in human populations, we have studied the allele frequency distributions of four STR loci (HUMTH01, HUMVWA31, HUMF13A1 and HUMFE S) in 16 different population surveys which can be categorised within three broadly defined ethnic groups: Caucasian, Asian (Indian subconti nent), and African (Afro-Caribbean and US black). We have observed tha t allele frequency distributions of populations within ethnic groups a re similar; consequently, genetic distances are an order of magnitude lower than between ethnic groups. Inbreeding coefficients (F-statistic s) and calculations of the number of mean heterozygous loci per indivi dual, along with estimates of variance, did not Suggest that the popul ations were substructured. This included a study of an immigrant Asian population known to comprise at least three different sub-groups. Fin ally, an indication of the discriminating power is given by calculatio n of likelihood ratios (LR) of each individual tested across all four loci. Approximately 70% of Caucasians give an LR of greater than 10,00 0; the test is even more discriminating in Afro-Caribbeans - approxima tely 90% of tests are greater than 10,000.