Table 2 summarizes the distribution according to the WT and the mutant allele, respectively. In four related individuals with a 3/4 genotype, all of whom were affected with RP, we were not able to deduct from the pedigree, or from other information available, if the 4-copy allele was the WT or the PRPF31-variant allele. These individuals are not included in Table 2 or in the analyses below. This evidence concerns the gene PRPF31 and retinitis pigmentosa 1.