X-linked retinitis pigmentosa: linkage with the centromere and a cloned DNA sequence from the proximal short arm of the X chromosome.

A large Danish pedigree segregating for X-linked retinitis pigmentosa (RPX) (Warburg and Simonsen 1968) was restudied for linkage analysis. Using two markers, i.e. the DNA base sequence polymorphism presented by the probe L1.28 defining the chromosomal segment DXS7, and the C-banding heteromorphism (Xcen) (Friedrich 1982), we were able to localize the RPX gene in Xp close to the centromere rather precisely. The gene order could be deduced by three-point linkage analysis, and the gene distances were determined by pairwise analysis using the LIPED program (Ott 1974). Together with previously published data concerning the RPX:DXS7 linkage (Bhattacharya et al. 1984) a regional gene map is constructed. Xcen-11 cM-RPX-6 cM-DXS7.