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If both my parents have black hair, is there a possiblity that I could have been a blonde?
Question Date: 2003-03-19
Answer 1:

There sure is. I don't want to get into a lot of technical words, so let's look at our set of genes like a recipe book.

We get one book from our mother, one from our father. Each has recipes for the same things, but sometimes there's a difference (mutation) in a recipe. Let's say I got a recipe for oatmeal cookies from both parents, but one recipe says to put in raisins and the other one doesn't. I'd still know to put in raisins because I have 2 copies. People who have black hair have at least one copy of the recipe (gene) for making black hair color (pignment). But they may also have one bad copy of the recipe. Which recipe they pass to you is a matter of chance. If both your parents have one copy of the good recipe, and one of the bad, they could pass on two bad recipes and you'd have blond hair. Or they could pass on two good recipes and you'd have black hair. Or they could pass on one good and one bad and you'd still have black hair. We call black hair the "dominant trait" because your hair is black even if you have only one copy. Blond hair would be the "recessive trait" because you need two bad recipes to have it.

Even though I'm calling the recipe bad (because it doesn't make pigment), there's nothing bad about having blond hair. It's just one of the many interesting differences between people. You may be wondering why I'm only talking about hair color as if there were two kinds, black and blonde. There are obviously more colors than that, caused by more variations in the recipes and other variations, but let's keep it simple for today.

If I tell you that brown eyes are dominant and blue eyes are recessive, can you tell me whether two brown-eyed people can have a blue-eyed child? Can two blue-eyed people have a brown-eyed child?

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