Dictionary of Human Evolution and Biology

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Color Blindness

Hereditary inability to distinguish one or more colors in the environment, independent of the ability to distinguish light, shape and form. Either red or green color blindness is the most common form of partial color blindness; both are rare, and owing to an interaction of recessive allele(s) at two loci (deutan and protan),both loci are on the X chromosome; mutations produce quantitatively defective opsins in the retina of the eye. A red-blind individual has protanopia and cannot produce the pigment erythrolabe. A green-blind individual has deuteranopia and cannot produce the pigment chlorolabe. A blue-blind individual has tritanopia and cannot produce the pigment cyanolabe: this is a much rarer form (aka blue opsin defect). Achromatopsia, the inability to discriminate among all colors of the rainbow (complete colorblindness) is sometimes found combined with other conditions such as myopia and cataracts. About 8% of the male and 0.4% of the female US population is affected. Roughly 75% of colorblind males have a defect in green opsin, while 25% have a defect in red opsin.

See tritanopia and complete color blindness.

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