Why do some people/namilas have one brown eye and one green eye?

I know, it's genetics - hey I wasn't sleeping through those grade 9 lectures on Mendel's peas. I know it happens often with huskies, I even knew that David Bowie has one blue eye and one brown eye - but I didn't know that Christopher Walken and Keifer Sutherland also have differently coloured eyes - but it kind of explains how they can look so weird in some roles. I also didn't know that Jane Seymour, Mila Kunis and Kate Bosworth also have heterchromia either - because that's what it's called when you have differently coloured eyes. It can be caused by genetics or injury.

Eye colour is made by cells called a melanocytes. If something happens to affect the melanocytes or the amount of melanocytes then eyes can be different colours. This can happen when the baby is in the womb. Eyes can also be different if people have different OCA2 genes for each eye because apparently OCA2 is the eye colour gene. There are also two other possible causes called mosaicism and Waardenberg syndrome but the coolest reason mismatched eyes can happen is called chimerism. That's when two fertilized eggs fuse to form one person - I saw something about that once on TV about a women who didn't have the same DNA as her children, even though she'd given birth to them.

Eyes can also look different because of injury - that's what happened to David Bowie - one of his pupils is permanently enlarged because of a bar fight he was in when he was young.

The more I learn about genetics, the more questions I have, but those questions will have to be explored another day.



http://www.thetech.org/genetics/ask.php?id=226