Polymorphism in the number of genes encoding long-wavelength-sensitive cone pigments among males with normal color vision.
Examination by direct DNA sequence analysis of the X-linked visual pigment genes in 27 males with normal color vision reveals that almost half have two or more different genes encoding a long-wavelength-sensitive cone pigment. This is counter to the conventional theory proposed from results of Southern hybridization studies that there is a single long-wave pigment gene per X-chromosome. Further, the sequences and consideration of the structure of the X-linked pigment gene array suggest that the majority of the observers (as many as 2/3) have hybrid (or fusion) genes like those that have been proposed to underlie color anomaly. In some observers the long-wave hybrid genes contain a substantial amount of middle-wave sequence, e.g. five observers have hybrid long-wave genes that contain middle-wave sequences that include exon 4. Three of those five have the hybrid as their only long-wave gene, and thus have no other gene that could potentially encode a long-wave pigment. In these subjects, it is the hybrid gene that produces their normal long-wavelength-sensitive cone pigment. The high frequency of hybrid genes indicates that they are normal variant forms of the long-wave gene. Contrary to what is commonly believed, the introduction and the expression of hybrid genes is not sufficient to cause color vision defects.
Neitz
M
M
Department of Ophthalmology, College of Wisconsin, Milwaukee, WI 53226-0509, USA. jneitz@post.its.mcw.edu
Neitz
J
J
Grishok
A
A
D001483:Base Sequence; D003118:Color Perception / Q000235:genetics*; D004247:DNA / Q000032:analysis; D005091:Exons / Q000235:genetics; D005784:Gene Amplification; D015870:Gene Expression; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D015183:Restriction Mapping; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism*; D012168:Retinal Pigments / Q000096:biosynthesis / Q000235:genetics*; D014960:X Chromosome
D012168:Retinal Pigments; D004247:DNA