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crissy2 · Oct 30, 2007, 12:18 PM

I'm confused about eye color. I have green eyes, both of my parents have blue eyes. I've been told that is impossible? My twins have dark brown eyes, my husband has blue and I have green. His dad has blue and his mother has hazel. I have read all about genes and used the eye calculator. Any answers?

firmbeliever · Oct 30, 2007, 12:29 PM

Are there brown eyed grandparents(your or your husbands) possibly?

templelane · Oct 30, 2007, 12:38 PM

Eye colour has a very complicated inheritance involving several genes (polygenic)
OMIM - EYE COLOR 1; EYCL1
This link states how in some families it is common for blue eyed parents to have brown eyed children.

This is due to different ways genes can be inhereted. It is not as simple as brown eyes dominant blue eyes recessive as it is often taught in school.

Also there is a process known as recombination whereby the genes reshuffle before they get divided up into gametes - the eggs and sperm. This can cause a person to inherit a working gene where the parents both had mutated ones - the manage to compensate for each other 'fixing' the code. This site explains it very well with picture which I can't do here!
Understanding Genetics: Human Health and the Genome

Another reason is random mutations although this is a much less likely. Or the environmet can affect eye colour, although this is also probably not the explanation here.

Can I ask are you of norwegein, swedish or other scadinavian extraction?

templelane · Oct 30, 2007, 12:51 PM

I would like to add that eye colour is not discrete as you have probably already noticed. It is caused by various levels of two pigments one yellow and another dark brown (sometimes termed black) there are many enzymes which regulate the expression of these pigments.

So say a blue eyed parent had the brown gene but not protein x which transports the pigment to a part of the cell where it can be seen. The other parent hasn't got the brown gene but has the transporter.

The child then inherits the brown gene from one parent and the transporter from the other so it has brown eyes et voila! brown eyed child blue eyed parents.

Disclaimer - Just to make clear this is a model and isn't necessary what happens, it is more likely protein x is an protein which modifies the pigment protein's expression levels.

margarita_momma · Oct 31, 2007, 11:27 AM

Originally Posted by firmbeliever

Are there brown eyed grandparents(your or your husbands) possibly?

That is what happened with my son. My ex-husband and I both have green eyes and so do our parents. His entire side of the family have green and blue eyes. The only person in my family with brown eyes is my grandmother so we say he got her eyes. It makes her so happy. :)

margarita_momma · Oct 31, 2007, 11:27 AM

Originally Posted by firmbeliever

Are there brown eyed grandparents(your or your husbands) possibly?

That is what happened with my son. My ex-husband and I both have green eyes and so do our parents. His entire side of the family have green and blue eyes. The only person in my family with brown eyes is my grandmother so we say he got her eyes. It makes her so happy. :)