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Name: Nick M.
Status: Educator
Age: 50s
Location: N/A
Country: N/A
Date: 2001

I have one biology student that has one blue eye and one brown or green (cannot remember which it is). How is this possible with all DNA carrying the same information?

Eye color is actually coded for by more than one gene. The process of eye color development entails a step by step process and is separate for each eye. It may be that one eye doesn't complete the whole process and stops one step short of full eye color development.


I have seen this in two people...I am not sure but here are some possibilities. First off, eye color is NOT as simple as the text books would have us believe. There are more than three genes involved. At least one for pigmentation and one for the thickness of the iris. Green is a transition I believe between blue and green. If one has a thicker iris and what might typically give pigmentation of blue one gets green . If the same amount of pigment is in a thin iris it results in blue. It is also quite possible that the genes are the same for both eyes but because of some developmental anomaly the lighter eye has had its ability to generate pigment interrupted.

Peter Faletra Ph.D.
Assistant Director
Science Education
Office of Science
Department of Energy

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