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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Evolution of color vision in primates ： ウィキペディア英語版 Evolution of color vision in primates 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 (cone cells), with spectral peaks in the violet (short wave, S), green (middle wave, M), and yellow-green (long wave, L) 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 (Old World monkeys and apes) are routine trichromats, meaning both males and females possess three opsins (pigments) sensitive to short-, medium-, and long wavelengths. In nearly all species of platyrrhines (New World monkeys) 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 (consistent) trichromats. ==Mechanism of color vision== 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Evolution of color vision in primates」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.