Figure 1. Pedigrees and 3q21 marker haplotypes spanning the RHO gene in autosomal recessive retinitis pigmentosa families RP21 (A) and RP53 (B). A: Family RP21 consists of four generations. White circles represent unaffected females, filled circles affected females, white squares unaffected males, and filled squares affected males. Deceased individuals are shown with a slanting line across the symbol. Also shown are the marker loci and their positions in an 18.5-Mb interval, which were used for fine mapping of the disease locus. Marker allele sizes were not accurately determined and therefore we only give two-allele designations. Arrowheads designate crossovers that define the 6.8-Mb minimal critical region between D3S1589 and D3S2322. B: Family RP53 consists of five generations. Patient V-3 in one branch of the family is homozygous for marker alleles flanking RHO. The disease in affected individual III-12 could be RHO unrelated, suggesting locus heterogeneity in the different branches of the family. Haplotypes were established for all individuals for which marker alleles are depicted, except for RP21-III-6, the haplotypes of whom were deduced (indicated with brackets around the haplotypes).