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Name: Korah E.
Status: Educator
Age: 40s
Location: N/A
Country: N/A
Date: October 2002

Our family appears to have several members who are blue-grey color blind. Another family member claims that there is no such condition, and that it is genetically impossible (two of the blue-grey color blind people are female). Is there such a form of color blindness, and can it be manifested in females? How does it work: which cones are not working/formed properly; how is the gene transmitted?

Color vision is determined by the cones in the retina in your eye. There are 3 types of cones. They each are responsible for a kind of color vision. It is kind of like having only 3 colors in a color ink cartridge, but the combinations and amounts can produce any color. The cones are coded for by different genes. Red Green color blindness is caused by a defect in a gene found on the X chromosome. But this is only one kind of color blindness, there are others involving the other sets of cones in the eye. I do not know which chromosomes those genes are found on, but it is possible for them genes to be found on other chromosomes than the X. And at any rate, just because a trait is sex-linked, it is possible for females to be affected if the mother is at least a carrier and the father is affected. It is true that if those women have fathers who are not affected, it is probably not sex-linked.


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