Identification of a novel polymorphism in the X-chromosome region homologous to the DYS456 locus

During an extensive multipopulation study with Y-short tandem repeat (STR) loci, amplified using the AmpFℓSTR® Yfiler™ PCR amplification kit, amplification of a 71 bp fragment was observed in 2.32% of the male samples analyzed (N=3141). By direct sequencing of this fragment, it was determined that the primer binding sequences were identical to those of the DYS456 locus. A T to G single-nucleotide polymorphism (SNP) enabled amplification of the 71 bp fragment. The SNP is located within an X-Y homologous region at Xq21.31 and was observed with the highest frequency within the African American and Sub-Saharan African populations in our study. Presence of SNP on the X chromosome did not interfere with the reliability of typing the DYS456 locus and the other Y-STR loci typeable using the AmpFℓSTR® Yfiler™ PCR amplification kit. Full profiles in a mixture of male:female at 1:4000 were obtained using the current configuration of the AmpFℓSTR Yfiler kit even in the presence of female DNA containing the G variant.