The ChrX-ChrY homologue non-recombining region are unique in the genome. Hosted on the ChrY this region can be transmitted only from father to son whereas the ChrX counterpart is inherited in the typical X-chromosomal mode. Doubtless, the most utilized locus of this type is the diallelic indel-polymorphism amelogenin, which is located at Yp11.1; Xp22.2 and is well-established for molecular gender assessment. Cali et al. (2002) described the locus DXYS156, which is located at Yp11.3 and Xq21.2-3. This marker is multi-allelic at both ChrX and ChrY. A Y-chromosome-specific nucleotide insertion in the duplicate STR allows males to be distinguished from females, as does the commonly used amelogenin system, but with the advantage that this locus, due to their multiple alleles, may contribute towards DNA fingerprinting of a sample. Yet another bonus is that both the X and the Y copies of DXYS156 have alleles specific to different parts of the world, offering separate estimates of maternal and paternal descent of that sample. It is of interest that some further markers of this kind have been published, namely DXYS241, DXYS265 and DXYS266 (Kotliarova et al., 1999; Lee et al., 2001). However, since they are dinucleotides they are sub-optimal in their use for forensic casework. Nevertheless, ChrX-ChrY homologue markers should attract more attention from the forensic community.
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