CRB1 and retinitis pigmentosa 1: This revealed 13 such regions of homozygosity greater than 1.5 Mb but only 4 of these regions contained obvious positional autosomal recessive RP candidate genes; CNGB1 (CFA2), RBP3 and RGR (CFA4), RD3 and CRB1(CFA7) and TULP1 (CFA12) (Table 1).