Eye Color in Children

Hi,

Welcome back to Medicine Mondays. This week I'm going to talk a little about eye color.
The following question from a loyal reader

Dear Dr. Cason-

Danger has blue eyes, but since the hubs and I both have green eyes,
his parents have green and brown and my parents have green and brown
what are the chances that her eyes with stay sooo blue?
If they are going to change will they usually do so by a certain age?- Nikki

Dear Nikki-

Great question! I have always wondered the same and have anxiously waited to see what color eyes my children would have.

You may remember learning about dominant and recessive traits (Patterns of Mendelian Inheritance) in high school. You learned that there are two copies of each gene that we inherit from each parent. For a recessive trait to show through, we must inherit two copies of the gene that codes for that trait - one from both our mother and father. Well we used to think that 'blue' was the recessive variant of the eye color gene, and 'brown' was the dominant variant. In other words, we used to think that a person's eyes would be brown even if they only inherited one 'brown' gene from either parent and blue only if they inherited both 'blue' genes from each parent.

Well now you can forget about these nice linear rules when it comes to eye color. It's not that easy. We now know that eye color is a polygenic trait which then determines the amount and type of pigments in the eye's iris.

Color variations among different irises are typically attributed to the melanin content within the iris. Most babies are born with blue eyes because they contain low amounts of melanin. As they get older their melanocytes darken and their eyes change color. By six months of age most babies will have their eye color set, but you can see some gradual changes in the color all the way up to 3 years of age.

In general, you can probably still say that blue eye color is recessive but truthfully the color of one's eyes are controlled by a variety of genes. You'd be hard pressed to accurately predict what color eyes your child will have. You'll have to wait until she gets a bit older. Personally all three of my kids had bright blue eyes. My oldest kept hers and the two little ones now have green eyes! They are all sooo pretty!