What Are The Chances My Baby Will Have Blue Eyes? A Genetic Explanation
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What color eyes will your baby have? When a new addition is on the way, it’s only natural to wonder about their appearance. Will your baby have blue eyes? There is no way to be totally sure, but you can make a good guess.
The Genetics of Blue Eyes
Blue is one of the rarest eye colors worldwide. The genetic mutation behind blue eyes actually switches off the gene that colors eyes brown and leaves them blue.
Everyone with blue eyes is related to a single, common ancestor. This ancestor most likely lived close to the Baltic Sea between six and ten thousand years ago.
The Genetics of Eye Color
The exact color of your baby’s eyes depends on how much melanin he produces. Melanin is the pigment that colors the human body. Eye color depends on how much of it is stored in the iris.
There are many different eye colors, existing along a continuum. The least amount of melanin produces blue eyes. More produces green eyes, and even more produces brown eyes, which is the most common eye color worldwide.
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Blue Eyes Aren’t Really Blue
Interestingly, blue eyes only appear that way. There is no blue pigment in the human iris or anywhere in the human body.
Varying levels of melanin are responsible for eye color. Melanin is brown, and little to no melanin makes the eyes appear blue. When light scatters, the longest wavelengths are blue, so that is what we see. This is the same reason that the sky and the ocean appear blue.
Ancestry as a Clue
Will your baby have any chance of being born with blue eyes? Look at your family background first. People with blue eyes usually have European ancestry. If either you, your partner, or anyone in your direct or second line of heredity (parents, grandparents, siblings, or aunts and uncles) has blue eyes, there is a chance that your baby could.
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Making Eye Color Predictions with Basic Genetics
If you want to try and predict your baby’s eye color, pull out your high school biology textbook to help narrow down just how likely it is that your baby will have blue eyes.
If you didn’t keep it, don’t worry, I’ll give you a quick review. As FamilyEducation’s Genetics Expert, I have developed my knowledge on these topics through a combination of college classes, teaching, and self-study.
We all inherit two copies of each gene (allele), eye color included. One copy comes from our mother, and one from our father. Both alleles are stored in our genetic code and can be passed on to our children, but only one presents in how we look.
Generally, darker colors dominate so a person with one brown-eyed gene and one blue-eyed gene will have brown eyes. The only way to present blue eyes is to inherit two copies of the blue-eyed gene. However, brown-eyed parents can pass a recessive blue-eyed gene. Therefore, two brown-eyed partners can birth a blue-eyed baby.
Here are the possibilities:
- Blue eyes + blue eyes = 100% chance of blue eyes
- Brown eyes + blue eyes = 50% chance of blue eyes, but only if the brown-eyed parent carries a blue-eyed gene. If not, the chance is 0%
- Brown eyes + brown eyes = 25%, but only if both parents carry the blue-eyed gene. If not, the chance is 0%
It is important to remember that this theory is a simplified version of what really happens at the genetic level. Human coloring is actually controlled by a complex genetic process and there are many different eye colors.
Still confused? Check out this handy baby eye color chart?
Predicting Your Baby's Eyes
Blue Eyes Are Not Always Here To Stay
Your baby could be born with blue eyes, but it might not stay that way. In fact, nearly all Caucasian babies have blue eyes at birth. In most cases; however, the eyes darker over the first year or two. Melanin production kicks in over time.
So will your baby be born with blue eyes? If you or others in your family have them, it is more likely. However, blue eyes are rare. And even if your baby is born with blue eyes, there is no telling if the color will stick.
Curious about other physical traits your baby will have? Here’s How to Predict Your Baby’s Hair Color.