Two anonymous X-specific human sequences detecting restriction fragment length polymorphisms in region Xq26→qter

Two anonymous X-specific sequences isolated from a genomic library of flow-sorted X chromosomal DNA were selected for study because they revealed restriction fragment length polymorphisms in the region Xq26 qter. One sequence, DXS10, detected a two-allele TaqI polymorphic system with allele frequencies of 0.33 and 0.67. The other, 4D-8, defined an Mspl polymorphism with allele frequencies of 0.18 and 0.82. DXS10 is tightly linked to the hypoxanthine phosphoribosyltransferase (HPRT)locus with recombination distance =0 cM at LOD=5.55 (95 % probability limit <15 cM). DXS10 maps to Xq26 but is not contained within the HPRTlocus itself. 4D-8 shows no detectable linkage to the HPRTlocus, with maximum likelihood estimate for =50 cM and a LOD score of –2.61 at = 5 cM. These two polymorphisms provide additional chromosomal loci for gene mapping by linkage at the distal end of the long arm of the human X chromosome.