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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