The STR cluster DXS10148-DXS8378-DXS10135 provides a powerful tool for X-chromosomal haplotyping at Xp22.

The evaluation of four pairs of tightly linked chromosome X (ChrX) short tandem repeat (STR)s at Xp22, Xq12, Xq26 and Xq28 led to the creation of the Argus X 8 multiplex amplification kit. These eight STRs are distributed as four closely linked pairs over the entire X-chromosome, and for practical reasons, they are assigned to four linkage groups 1-4. To achieve a further considerable enhancement in discrimination power, we suggest to include additional markers. A recent paper referred to the earlier evaluation of STR clusters at Xq12, Xq26 and Xq28, and here we present the pending data of linkage group 1 at Xp22. The newly established STR updates the Xp22 STR cluster which now presents three polymorphic markers: DXS10148 (PIC = 0.8556), DXS10135 (PIC = 0.9093) and DXS 8378 (PIC = 0.6454). Typing of 398 X-chromosomes provided 278 different and 200 unique haplotypes. All the other haplotypes observed appeared with frequencies in the range between 0.005 and 0.015. Considering this STR triple in the context with the three further triple clusters Xq12, Xq26 and Xq28 published earlier, we announced the development of a next generation of a ChrX STR cluster typing kit.