This model doesn't explain green eyes for example. Now eye color is obviously more complicated than this. But they can pass a “b” down to their kids, who might end up with blue eyes. Since blue is recessive to brown, Bb people have brown eyes. This means there are three possible combinations for this eye color gene: BB, Bb, and bb.īB is of course brown and in this model, bb would be blue. See, we have two copies of each of our genes - one from each biological parent. This matters because it is an explanation for how brown-eyed parents can have a blue-eyed child. The model also said that blue (b) was recessive to brown (B). Geneticists represented the brown version as “B” and the blue version as “b”. A big part of the model was the idea that we had an eye color gene that came in two varieties - brown and blue.
And You Thought a Two Gene Model was Complicated.Įye color used to be presented as a fairly simple trait. That something is most likely other genes involved in eye color that we don't know about. Too rare to explain all the exceptions we see with eye color.
So if a change happened that turned a blue eye color gene into a brown one, then blue-eyed parents could have a brown-eyed child.Īs you might guess, this sort of thing is pretty rare. But as with anything genetic, there are always exceptions.įor example, DNA can and does change between generations. Now we aren't being dishonest or trying to hide anything by presenting this model. Blue-eyed parents can have kids with brown eyes. In fact, this is the model we used for our eye color calculator.* And that we talk about extensively here at Ask a Geneticist. Which makes it impossible for two blue-eyed parents to have a brown-eyed child - they don't have a brown eye gene to pass on! This means that if a parent has a brown eye gene, then that parent will have brown eyes.
This has to do with the fact that blue eyes are supposed to be recessive to brown eyes. We were all taught that parents with blue eyes have kids with blue eyes. If you stayed awake during high school biology, you might find this answer surprising. Yes, blue-eyed parents can definitely have a child with brown eyes.
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