title: Genetic basis of photopigment variations in human dichromats.
abstract: The spectral sensitivities of the X-encoded pigments in dichromats were studied using the electroretinogram. The action spectra measured for these subjects correspond to four distinctly different X-encoded visual pigments, two different middle-wave pigments spectrally separated by 7 nm and two different long-wave pigments separated by 5 nm. Amino acid sequences were deduced from examination of the genes encoding the pigments. Pairwise comparisons of the opsin structures and pigment spectra confirm and clarify earlier conclusions. Substitutions in exon 5 of the genes produce the spectral difference that separates human X-encoded pigments into middle- and long-wave classes. Polymorphisms in exons 2-4 produce subtypes of pigments that fall within those major classes. Substitution of half of a middle-wave gene with long-wave sequence (exons 1-3) does not shift the middle-wave spectrum. Combined substitutions at positions 230, 233 and 180 produce a 7 nm shift in the in the middle-wave pigment spectrum. Two subtypes of long-wave pigments that differ in the presence of serine or alanine at position 180 and occur in dichromats, deuteranomalous trichromats, and color normals are spectrally separated by 5-7 nm.
authors.affiliation: Department of Ophthalmology, Medical College of Wisconsin, Milwaukee 53226, USA.
authors.forename: M
authors.initials: M
authors.lastname: Neitz
authors.forename: J
authors.initials: J
authors.lastname: Neitz
authors.forename: G H
authors.initials: GH
authors.lastname: Jacobs
mesh_terms: D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D003117:Color Vision Defects / Q000235:genetics*; D004247:DNA / Q000737:chemistry; D004596:Electroretinography; D005091:Exons; D008040:Genetic Linkage; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012168:Retinal Pigments / Q000737:chemistry / Q000235:genetics*; D013053:Spectrophotometry; D014960:X Chromosome
chemical_list: D012168:Retinal Pigments; D004247:DNA