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The four pigments in a bird's cone cells (in this example, estrildid finches) extend the range of color vision into the ultraviolet. [1]Tetrachromacy (from Greek tetra, meaning "four" and chroma, meaning "color") is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye.
Both of these alleles are expressed due to x-inactivation (one kind of X chromosome will get expressed in some photoreceptor cells, whereas the other kind of X chromosome will get expressed in the other photoreceptor cells) so a carrier will have 4 distinct cones with different spectral sensitivities, which is one prerequisite of tetrachromacy. [1]
Color blindness or color vision deficiency (CVD) is the decreased ability to see color or differences in color. [2] The severity of color blindness ranges from mostly unnoticeable to full absence of color perception.
A remote vertebrate ancestor of primates possessed tetrachromacy, [1] 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 most mammals are strictly dichromats , the exceptions being some primates and marsupials ...
This inferred a photopic cone-driven system that was at least marginally functional. The methodology did not investigate novel color vision, though one respondent claimed to more easily interpret traffic lights. [9] This may be considered the first case of a cure for colorblindness in humans.
Munsell color system – early perceptually-uniform color space; Natural Color System (NCS) – perceptual; Pantone Matching System (PMS) – standardized color reproduction (and color list) RAL – standardized color matching (and color list) Aerospace Material Specification – Standard 595A (Supersedes (US) Federal Standard 595C) [13]
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Jameson et al. [14] have shown that with appropriate and sufficiently sensitive equipment it can be demonstrated that any female carrier of red–green color blindness (i.e. heterozygous protanomaly, or heterozygous deuteranomaly) is a tetrachromat to a greater or lesser extent.