Figure 3. Identification of L7Q mutation in connexin 50 of Dca rats. A: F2 (SHR-Dca x PD) animals (n=93) are categorized according to their genotypes, with number of animals in each category below. Alleles of SHR-Dca origin are indicated in white, alleles of PD origin are in dark gray, and heterozygous state is indicated by medium gray color. The corresponding linkage map with distances in cM (Kosambi map function) is shown on the right. The Dca gene is inherited in a Mendelian fashion as semi-dominant (ratio in F2 1:2:1, microphthalmia:cataract:normal, χ²=0.96, p=0.62). Dca maps to chromosome 2. There is no recombination between Dca and D2Arb20. The critical interval containing the Dca gene is localized between D2Rat134 and D2Rat186 and spans 3.9 cM. The corresponding chromosomal segment has 8.6 Mbp. B: Sequencing of the Gja8 gene is shown. A mutation (T to A transversion in codon 7 of Cx50) results in the substitution of leucine for glutamine (L7Q) in Dca/Dca animals. +/Dca heterozygotes are also heterozygotes for L7Q.