Molecular genetics of the middlewave and longwave sensitive opsin genes of higher primates

Over the 10 year period since the cone opsin genes of humans were first isolated and sequenced, a wealth of information has accumulated on the genetics of primate colour vision. However, a number of intriguing questions have remained unanswered. Do other apes and monkeys see with the same basic complement of photopigments as humans do. How are these different opsin genes temporally and spatially regulated. At present a complete understanding of human colour anomalies is lacking. Based on the analysis of exons 3 to 5 of the X-chromosome opsin genes of two members of the Hominidea (the chimpanzee, Pan troglodytes and the Gorilla, Gorilla gorilla) and five members of the Cercopithecoidea family of Old World primates (the Diana monkey, Cercopithecus diana; lesser spot-nosed guenon, Cercopithecus petaurista; African green monkey, Cercopithecus aethiops; talapoin monkey, Miopithecus talapoin; and patas monkey, Erythrocebus patas), it is predicted that the long-wave (LW) and middle-wave (MW) pigments of these primates have similar spectral properties to those of human. Multiple copies of the same opsin gene sequence were identified in the chimpanzee and talapoin. Humans and the other primates show a bunching of polymorphic sites in exon three. The ancestry of the separate LW and MW genes of Old World primates is discussed. Two anomalous trichromatic human males, each exhibiting the same phenotype, were found to present with differing genotypes. One subject, SSJ, possessed a normal LW and a MW-LW hybrid gene. The other subject, PSJ, had in addition a normal MW gene. It is suggested that the same phenotype may be possible due to selective expression of some of PSJ's opsin genes. Finally, the phenotype of John Dalton, considered the father of colour vision, has been revised to deuteranopia, following amplification, cloning, and sequencing of his opsin genes from the remains of his eyes