Now the child has blue eyes.īut how can a brown eyed person pass a “clear card?” It is because we have two copies of most of our genes. The blue stays hidden until two people with a hidden blue happen to both pass a clear and a blue to their child. Generation after generation, at least one parent passes down a brown version of the first gene. This is a very simplified version of how blue eyes can stay hidden in a family tree. But if you have a clear card (not-brown gene), then the second card (gene) matters. Here is what I mean:Īs you can see, if you have the brown card (gene), you will have brown eyes no matter what is underneath.

Now you have blue or green eyes depending on the underneath card.

If you have the clear card, then you can see what is underneath. It could be green, it could be blue…who knows? The end result is brown eyes. If you have a brown card, you can’t see the card underneath. This first gene comes in two versions, brown and clear. Imagine the first gene is a card that is always on top of the second one. This gene will determine whether you will have green or blue eyes. If it says not to have brown eyes, then the second gene kicks in. If it says have brown, then the other gene doesn’t matter. The first gene determines whether or not you will have brown eyes. Even the simplest models of eye color that try to explain just brown, green, and blue need two genes. Well, that is almost how it worked… Three Eye Colors, Two Genesįor something seemingly so simple, eye color is surprisingly complex. You and your husband both have blue and at least one of you has green eyes hiding behind your brown.īy chance, you each passed a blue to one of your children and that child ended up with blue eyes.

This is almost certainly how the two of you ended up with a child with blue eyes. Now their children would have a chance at blue eyes. The blue eyes would keep getting passed down until finally one of these “carriers of blue eyes” had children with another parent that was a carrier too. Blue eyes can stay hidden in a family tree for hundreds of years Now, generation after generation, everyone will have brown eyes and some will have those hidden blues. Only one parent in each generation has blue hidden behind his or her brown. This is one way that blue eyes can stay hidden for hundreds of years before making a sudden, dramatic appearance. But these kids could all still have blue hiding behind their brown like that parent. If only one parent has the right stuff to pass on blue eyes, odds are none of the kids will end up with blue eyes. That right time is when both parents happen to have that particular color hiding out behind their brown. The blue eyes could still be hiding there, waiting for the right time to appear. This is true even if an eye color like blue hasn't been seen in a family for generations. While the truth is more complicated than described below, it is still true that brown eye color is more dominant to blue, and that the DNA for blue eyes can be hidden in a family for generations.Ī lot of different colors can lurk behind someone's brown eyes. Eye color is a complex trait that is influenced by many genes. While it describes eye color as a simple trait determined by 2 genes, scientists now know this is incorrect. Editor’s Note (): Some information in this article is out of date.

Black baby girl with blue eyes