The genes that encode the opsins (q.v.) synthesized by the cone cells of the retina (q.v.). The table compares the three CPGs of humans. The green and red CPGs differ by only 15 codons. The genes lie in tandem, with the red CPG farther away from the telomere of Xq. The green CPG may be present in two or three copies, the result of unequal crossing over (q.v.). This has also produced hybrid genes that contain coding sequences from both red and green CPGs. An upstream sequence, 4 kilobases from the red gene and 43 kilobases from the green gene, is essential for the activity of both. Deletions of this 580 base pair element result in a rare form of X-linked color blindness that is characterized by the absence of both red and green cone sensitivities. The blue opsin shows about 40% amino acid sequence identity with either green or red opsins, and the identity value is similar when the blue opsin and the rod cell opsin are compared. All catarrhine primates (q.v.) have the three cone pigment genes mentioned. In contrast, platyrrhine monkeys (q.v.) have only one X-linked and one autosomal color photopigment gene. See Chronology, 1986, Nathans et al.; color blindness, rhodopsin (RHO).
Cone Pigment Genes
Coding length (bp)
Total intron length (bp)
Subjects: Genetics and Genomics.