[Molecular genetic examination in sex-linked color blindness].

The molecular structure of the X-linked colour-vision locus was studied in a family where mild red-green colour-vision deficiency (deuteranomaly) segregated, and in a male with complete absence of red and green colour-vision (blue cone monochromasy). In individuals with normal colour-vision the red and green pigment genes had normal molecular structure whereas individuals with deuteranomaly, in addition to normal red and green genes, also had an abnormal hybrid gene consisting of parts of the green and red pigment genes. The individual with blue cone monocromasy had only a red-green hybrid gene inactivated by a critical mutation in codon 203. Thus, the phenotypes predicted from the individual genotypes were in complete accord with the observed phenotypes.