New markers for linkage analysis of X-linked hypophosphataemic rickets

Three polymorphic markers have been used to improve the genetic map of the region Xp22.1-p22.2, which contains the HYP (hypophosphataemic rickets) locus. DXS365 gave no recombinants with HYP, with a peak Lod score of 5.4 at theta = 0.0. A microsatellite marker mPA274 was derived for the DXS274 locus; it detects five alleles with a polymorphism information content of 0.55. Combining information from this microsatellite and the original DXS274 marker, probe CRI-L1391, the peak Lod score for DXS274 against HYP was 9.6 at theta = 0.02. A microsatellite associated with the DXS207 locus (mPA207) gave a peak lod score against HYP of 4.7 at theta = 0.14. A consideration of key recombinants and multilocus analysis suggests the gene order. Xpter-DXS207-DXS43-DXS197-(DXS365,HYP)- DXS274-DXS41-Xcen.