Deuteranomalous trichromacy in a subject revealing only an L-cone pigment gene

Abstract

A 19-year-old male was shown to have a deutan defect when he was examined with the FM-100 hue test (186 errors). The subject's performance on the Nagel anomaloscope was consistent with that of a person with deuteranomalous trichromacy: His match point was broad and shifted towards the green end of the red/green scale (10-40). However, southern blot analysis of the subject's DNA by means of probes for the X-linked photopigment genes revealed an absence of the restriction fragments characteristic of M-cone pigment genes. By this analysis, the subject should have deuteranopia. The differences between the psychophysical and molecular genetic results cannot be accounted for by rod intrusion into the subject's color matches: The quantal match predicted by rod and L-cone pigments falls outside the subject's anomaloscope match range. These results suggest that there are M-cone photopigment genes that are missed by conventional molecular genetic analysis.</jats:p