I am an African-American. Why do I have blue eyes?

African-Americans with blue eyes are not unheard of, but they are pretty rare. There are lots of ways for this to happen. Some possible ways an African-American person might have ended up with blue eyes are:

1. Caucasian relatives in their ancestry (the most likely reason)
2. A rare disease that causes albinism only in the eyes (ocular albinism)
3. A new mutation that makes their eyes blue
4. Waardenburg syndrome (A common way to end up with two different colored eyes.)

Ocular Albinism

Let's get rid of one of these reasons pretty quickly: you probably don't have a rare form of albinism called ocular albinism (OA).

Albinism comes about when your body fails to make melanin, the pigment that gives skin, hair, and eyes their dark color. In some forms of albinism, only the eyes are affected.

There are a number of reasons why you probably don't have OA. People with OA tend to have very poor eyesight, something you didn't mention in your description. Also, they probably would have tested you for this and told you about it at the Georgia Eye Institute.

The final reason is that you are a woman. Like colorblindness or hemophilia, OA happens mostly in men.

Waardenburg Syndrome

Similarly to OA, it’s unlikely that you have Waardenburg Syndrome. This is a rare genetic condition that causes a number of symptoms in addition to blue eyes, including hearing loss, different-colored eyes, and a white patch of hair on the forehead.

If you had Waardenburg Syndrome there’s a good chance that you would have one of these other symptoms, or it would have been discovered at the Georgia Eye Institute.

European Ancestry

If not a rare genetic condition, then what about the other possibilities? It is possible that there are white relatives on both your mother's and your father's side of the family. You need to have Caucasian relatives on both sides of your family, for reasons that I will explain here. It can sometimes take many generations for a trait like blue eyes to pop up in the family tree again.

The reason it can take a few generations to see something like blue eyes is that it is partly caused by a recessive gene.To help understand how this works, let's give an example. Our example simplifies eye color too much (the genetics of eye color are more complicated) but it'll make the same point.

Remember that for most genes, you have two copies of each gene, one inherited from your mother and the other from your father. The brown version of the eye color gene (B) is dominant over the recessive blue version (b). Dominant means that if either of your genes is the B version, then you will have brown eyes -- blue is recessive to brown. Genetically speaking, people with brown eyes can either be BB or Bb, but people with blue eyes can only be bb.

How could two brown-eyed people have a blue-eyed baby? The most likely way is if both were carriers for blue eyes (Bb). Each parent could contribute a b version of the gene so that the child would be bb and have blue eyes. If a single gene were involved, the chances for a blue-eyed child would be 1 in 4.

One of the ways blue eyes can stay "hidden" for a long time is if there are always marriages between Bb (brown eyed carriers of blue eyes) and BB folks. You can only get brown eyes from this mix -- the BB parent can only contribute the dominant B gene.

The genetics involved are actually even more complicated, making it even harder to get blue eyes. There are at least two, and probably more, genes that contribute to eye color. All of your copies have to be the blue kind to get blue eyes. This makes blue eyes rarer still.

New Mutations

What if there are no white ancestors in your family background? Another possibility is that a key eye color gene was mutated or changed in you so that you now have blue eyes. These sorts of mutations are very rare, but it is where all the wonderful variety of people you see around you originally came from. You may be a genetic pioneer!