Genetics and evolution of ultraviolet vision in vertebrates.

Various vertebrates use ultraviolet (UV) vision for such basic behaviors as mating, foraging, and predation. We have successfully interchanged the color-sensitivities of the mouse UV pigment and the human blue pigment by introducing forward and reverse mutations at five sites. This unveils for the first time the general mechanism of UV vision. Most contemporary UV pigments in vertebrates have maintained their ancestral functions by accumulating no more than one of the five specific amino acid changes. The avian lineage is an exception, where the ancestral pigment lost UV-sensitivity but some descendants regained it by one amino acid replacement at an entirely different site.