The "evolution of color vision in primates" is unique compared to most eutherian mammals. A remote vertebrate ancestor of primates possessed tetrachromacy, but nocturnal, warm-blooded, mammalian ancestors lost two of four cones in the retina at the time of dinosaurs. Most teleost fish, reptiles and birds are therefore tetrachromatic while all mammals, with the exception of some primates and marsupials, are strictly dichromats. Primates achieve trichromacy through color photoreceptors , with spectral peaks in the violet , green , and yellow-green wavelengths. Opsin is the primary photopigment in primate eyes, and the sequence of an organism's opsin proteins determines the spectral sensitivity of its cone cells. Not all primates, however, are capable of trichromacy. The catarrhines are routine trichromats, meaning both males and females possess three opsins sensitive to short-, medium-, and long wavelengths. In nearly all species of platyrrhines males and homozygotic females are dichromats, while heterozygotic females are trichromats, a condition known as allelic or polymorphic trichromacy. Among platyrrhines, the exceptions are "Alouatta" and "Aotus", both of which are uniform trichromats. Genetically, there are two ways for a primate to be a trichromat. All primates share an S opsin encoded by an autosomal gene on chromosome 7. Catarrhine primates have two adjacent opsin genes on the X chromosome which code for L and M opsin pigments. In contrast, platyrrhines have only a single, polymorphic X chromosome M/L opsin gene locus. Therefore, every male platyrrhine is dichromatic because it can only receive either the M or L photopigment on its single X chromosome in addition to its S photopigment. However, the X chromosome gene locus is polymorphic for M and L alleles, rendering heterozygous platyrrhine females with trichromatic vision, and homozygous females with dichromatic vision. Wiz Science™ is "the" learning channel for children and all ages. SUBSCRIBE TODAY Disclaimer: This video is for your information only. The author or publisher does not guarantee the accuracy of the content presented in this video. USE AT YOUR OWN RISK. Background Music: "The Place Inside" by Silent Partner (royalty-free) from YouTube Audio Library. This video uses material/images from https://en.wikipedia.org/wiki/Evolution+of+color+vision+in+primates, which is released under Creative Commons Attribution-Share-Alike License 3.0 http://creativecommons.org/licenses/by-sa/3.0/ . This video is licensed under Creative Commons Attribution-Share-Alike License 3.0 http://creativecommons.org/licenses/by-sa/3.0/ . To reuse/adapt the content in your own work, you must comply with the license terms.

• published: 24 Sep 2015
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