Tetrachromacy
Many people are aware that mutations in the eyes can cause color blindness, but not so many know that there are mutations that can cause “super human” vision. Tetrachromacy is a condition that causes people to have an extra cone in their eye, which causes them to be able to perceive more colors than the average person. Previously it was believed that only animals such as fish, birds, and insects had this ability, but now it is clear that some women have it. People with normal color vision are able to differentiate between about one million different shades of colors, while tetrachromatic people are able to see about 100 million different shades.
Tetrachromacy is caused by a similar mutation, on the X chromosome, to the one that causes color blindness, however this condition effects mostly women compared to color blindness that effects mostly men. Studies show that women with this condition are almost always the mother or daughter of a color blind man, which shows the correlation between the two disorders. (Greenwood, 2012)
It is believed that about 12% of women are carriers of the X-linked color vision deficiency mutation. The strange thing is that only 4% of these women exhibit tetrachromacy. This means that less than 0.5% of women actually have this ability, however, more research is necessary to come up with an accurate number of how common this disorder is. It is still unknown why only a fraction of women with four cones are tetrachromatic. (Jordan, 2010)
Tetrachromacy is caused by a similar mutation, on the X chromosome, to the one that causes color blindness, however this condition effects mostly women compared to color blindness that effects mostly men. Studies show that women with this condition are almost always the mother or daughter of a color blind man, which shows the correlation between the two disorders. (Greenwood, 2012)
It is believed that about 12% of women are carriers of the X-linked color vision deficiency mutation. The strange thing is that only 4% of these women exhibit tetrachromacy. This means that less than 0.5% of women actually have this ability, however, more research is necessary to come up with an accurate number of how common this disorder is. It is still unknown why only a fraction of women with four cones are tetrachromatic. (Jordan, 2010)
Women with a functional extra cone in their eye are able to perceive wavelengths of light that ordinary people can not. These wavelengths are usually between the wavelengths that the medium and long cones can perceive, and let functional tetrachromats see many shades of yellow.
It is hard to diagnose tetrachromacy, because there is not much research done yet and the testing is hard to pinpoint. However, there are a few tests that can be done to determine if someone is a tetrachromat, such as a test which includes many different shades of somewhat similar colors that have to be put in order. This can be very difficult for people with normal vision, but tetrachromats have no problem distinguishing the differences in the shades. There are also genetic tests that can be done to confirm that women have the special gene on their 23rd X chromosome that provides evidence of a fourth cone.
There is hope that future research on tetrachromacy can lead to a cure for color blindness, but much more research has to be conducted before this can be considered. Right now studies are trying to figure out why only a small fraction of women with a fourth cone are tetrachromatic, with a current theory being that some people do not have the flexibility in their visual system to compensate for the extra cone. Only a handful of women have been diagnosed as tetrachromats and no men to date have been, so research on this condition is still in the early stages.
It is hard to diagnose tetrachromacy, because there is not much research done yet and the testing is hard to pinpoint. However, there are a few tests that can be done to determine if someone is a tetrachromat, such as a test which includes many different shades of somewhat similar colors that have to be put in order. This can be very difficult for people with normal vision, but tetrachromats have no problem distinguishing the differences in the shades. There are also genetic tests that can be done to confirm that women have the special gene on their 23rd X chromosome that provides evidence of a fourth cone.
There is hope that future research on tetrachromacy can lead to a cure for color blindness, but much more research has to be conducted before this can be considered. Right now studies are trying to figure out why only a small fraction of women with a fourth cone are tetrachromatic, with a current theory being that some people do not have the flexibility in their visual system to compensate for the extra cone. Only a handful of women have been diagnosed as tetrachromats and no men to date have been, so research on this condition is still in the early stages.