NEW MARKERS FOR LINKAGE ANALYSIS OF X-LINKED HYPOPHOSPHATEMIC RICKETS

Three polymorphic markers have been used to improve the genetic map of the region Xp22.1-p22.2, which contains the HYP (hypophosphataemic ri ckets) locus. DXS365 gave no recombinants with HYP, with a peak Lod sc ore of 5.4 at theta = 0.0. A microsatellite marker mPA274, was derived for the DXS274 locus; it detects five alleles with a polymorphism inf ormation content of 0.55. Combining information from this microsatelli te 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 asso ciated with the DXS207 locus (mPA207) gave a peak lod score against HY P of 4.7 at theta = 0.14. A consideration of key recombinants and mult ilocus analysis suggests the gene order: Xpter-DXS207-DXS43-DXS197-(DX S365, HYP)-DXS274-DXS41-Xcen.