The polymorphic photopigments of the marmoset: spectral tuning and genetic basis.

The marmoset (Callithrix jacchus jacchus), a South American monkey, is polymorphic for the middle- to long-wave cone photopigments: the three variant pigments have spectral peaks at 543, 556 and 563 nm. Comparisons of the deduced amino acid sequences of these pigments indicate that the variations in spectral sensitivity are associated with the presence or absence of hydroxyl-bearing residues at sites 180 and 285; but, in contrast to the additive hypothesis of Neitz et al. (1991), we propose that adjustments at site 233 may also be required to produce viable long-wave and middle-wave pigments. Within a family group of monkeys, we find that a restriction site polymorphism in the photopigment gene segregates in a way that is consistent with the single X-linked gene hypothesis previously proposed on the basis of the photopigment types present in male and female marmosets.