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A color blindness gene is a gene linked with colorblindness. Over 50 genes have been associated with color blind genetic traits, and many of them are found on the X chromosome, leading people to consider color blindness an example of an X or sex-linked trait. Like other X-linked traits, color blindness is far more common in men than women, a reflection of the fact that men need only inherit one copy of the color blindness gene for it to manifest, because their shortened Y chromosomes don't have a clean copy of the gene to override the defective one.
There are three different forms of color blindness. The most mild is anomalous trichromacy, where people can see colors relatively normally, with small distortions. The severity varies, but the patient has full color vision and some patients have such a subtle case that they may not realize their color vision is not entirely normal. In dichromancy, people are capable of some color distinction, but not all. A common example is red-green color blindness, and people can also have tritanopia, or blue-yellow color blindness.
The most severe form, monochromacy, is also very unusual. In people with this form, all hues cannot be distinguished and the world is seen in shades of light and dark. All three types of color blindness can have genetic causes. A color blindness gene may cause problems with visual perception alone, or may cause it in association with other genetic issues. Some examples of genetic conditions known to be associated with color blindness are rod-cone dystrophy, retinitis pigmentosa, and blue cone monochromatism.
A single color blindness gene can be enough to cause problems with visual perception and some people may inherit several faulty genes. These genes can also be passed on to children, making the children carriers or colorblind themselves, depending on the gene and the sex of the child. In families with a history of color vision problems, the genetic inheritance can be traced to see who is a carrier and find out when the gene entered the family.
Identifying a color blindness gene has been hindered by the complexity of human vision and the understanding that many different genes can be involved in color perception. Finding out which genes are associated with various forms of color blindness opens the possibility to gene therapy, where people could be treated to restore color vision. Some successful experiments with gene therapy in monkeys have shown promise for human medicine and the management of color blindness in human communities.