Sequence divergence, polymorphism and evolution of the middle-wave and long-wave visual pigment genes of great apes and Old World monkeys.

In man, the spectral shift between the middle-wave (MW) and long-wave (LW) visual pigments is largely achieved by amino acid substitution at two codons, both located in exon 5. A third amino acid site coded by exon 3 is polymorphic between pigments. We have studied the equivalent regions of the cone opsin genes in two members of the Hominidea (the gorilla, Gorilla gorilla and the chimpanzee, Pan troglodytes) and in three members of the Cercopithecoidea family of Old World primates (the diana monkey, Cercopithecus diana, the talapoin monkey, Miopithecus talapoin, and the crab-eating macaque, Macaca fascicularis). No variation in the codons that specify the amino acids involved in spectral tuning were found. We predict therefore that the MW and LW pigments of gorilla and chimpanzee have similar spectral characteristics to those of man. Multiple copies of the same opsin gene sequence were identified in the chimpanzee, talapoin and macaque and we also show that non-human Old World primates are similar to man in showing a bunching of polymorphic sites in exon 3. We discuss the ancestry of the separate MW and LW genes of Old World primates and the equivalent polymorphic gene of the marmoset, a New World primate.