The clinical findings defining the diseases as a cone-rod dystrophy rather than cone degeneration also support the exclusion of CNGB3, CNGA3 and GNAT2. The candidate loci CORD8 and CORD9 are not yet mapped and the genes remain to be identified, but the markers typed for these loci are located within 2.8 Mb of the gene and several recombinations exclude these loci as well. This evidence concerns the gene GNAT2 and Cone rod dystrophy.