Looking at the photo to your left — the one of that very bald, very blue-eyed baby girl of mine — it’s hard to imagine that at one point in the first six weeks of her life, I insisted that I thought her eyes were going to be brown. Everyone to whom I mentioned this prediction guffawed, pointing out that both Jon and I have blue eyes (both of us actually have incredibly unremarkable blue/grey eyes), thus making it genetically impossible for me to throw a brown eyed baby.
But wait, I thought to myself, neither of my parents have brown eyes (father-blue, mother-green) and yet my little brother’s eyes are as brown as brown can be. So unless we want to believe that a brown-eyed milkman had some role in my brother’s genetic make-up, that means that two parents without brown eyes can indeed have a baby with brown eyes.
I was a terrible science student in high school and college. I barely made it through the basic biology classes I was required to take. I remember finding the study of genetics particularly confusing, but as I continued insisting that Baby G’s eyes might be brown, and as people kept telling me that simply wasn’t possible, I thought I remembered hearing my college biology professor explain that two brown eyed parents could theoretically produce a blue eyed child. Still, friends and family kept teasing me about my stubborn insistence that it was even POSSIBLE that G’s eyes would be brown, so I decided to do some Googling.
It turns out that I was, in fact, correct: it’s completely possible for parents who share the same eye color to produce a child with a completely different eye color.
Most of us learned the model for determining eye color that G.C. Davenport and C.B. Davenport devised in 1907. The Davenport model wrongly says brown eye color is always dominant over blue eye color, which means that two blue-eyed parents always have blue-eyed kids. We know better now.
“Although not common, two blue-eyed parents can produce children with brown eyes,” says Richard A. Sturm, a Principal Research Fellow at the Institute for Molecular Bioscience at the University of Queensland in Brisbane, Australia.
Eye color is a complex trait that depends on the state of several interacting genes. The gene that usually decides the issue (blue eyes or brown eyes) is the OCA2 gene on chromosome 15. But it comes in different strengths. A person with a weak form of the OCA2 gene will have blue eyes. Likewise a person with a strong form will have brown eyes.
The plot thickens, though, because an individual also has other eye-color genes that each has a say in the final eye-color outcome. For example, if one of these lesser genes is strong, it can make the weak form (blue) of OCA2 work much more effectively — almost like the strong form (brown). Then the eye color may be a light brown or muddy grey. In fact, the resulting color can be any shade of brown, hazel/green, or blue depending on the strengths of the interactions.
Yes… Two brown-eyed parents can have a blue-eyed child. In fact, this is fairly common.
Aha! I adopted a very self congratulatory tone as I shared this info with all the naysayers who were telling me that there was no way I could be right about newborn Baby G’s eyes being brown. But then, of course, her eyes began getting blue-er and blue-er, and by 8 weeks of age, the child had eyes the color of Cookie Monster’s fur. Totally blue. Unquestionably blue. So I had been right about the genetics but wrong about my baby’s actual eye color. Oh well.
But it was interesting for me to confirm my understanding that two people CAN give birth to a child with totally different eye color.
What color are your baby’s eyes, and how do they compare to the rest of the family?