X-STR diversity patterns in the Finnish and the Somali population

Autosomal and Y-chromosomal STR markers have been routinely used in kinship analyses already for over a decade, augmented by mitochondrial DNA in more complex cases questioning the maternal relationships of the samples. Recently, a commercial X-chromosome typing kit Mentype Argus X-8 was introduced to supplement the existing forensic toolkit. In this study, X-STR allele frequencies and population diversity indices in two ethnic groups, the Finnish and the Somali, are reported. Several previously unreported alleles and features in the allelic distribution were observed, some of which were further investigated with a small set of family data. Most notably, several alleles showed significant frequency differences between sexes, yet no obvious explanation for this discrepancy was found. As a demonstration of X-chromosome analysis in practice, we describe two family reunion cases, where the X-STR data was successfully utilized.