The Genetics of Human Skin Color
Caucasians Are Fair-Skinned Because of the Golden Gene
A genetic study in zebrafish helps to identify the gene responsible for Europeans' pale skin-the golden gene.
Back in 2006, a woman who gave birth to twin baby girls was a big story. This kind of thing isn’t usually a big deal. Except when one girl looks African and the other Caucasian.
We do not understand the genes involved in human skin color enough to know for sure how this happened. But a recent zebrafish study has helped scientists find one of the genes that is almost certainly involved.
Caucasian Zebrafish
When people study zebrafish, a common variant they use has golden stripes instead of the usual black. No one had ever figured out why these fish had yellow stripes.
In late 2005, a group of researchers led by Dr. Cheng at Penn State finally got around to finding the gene that was mutated in these fish. And when they found the same gene in people, they discovered that most Europeans all shared mutations in the same gene. They named the gene they discovered SLC24A5. Since then it has been renamed golden.
Having Two Different Colored Twins
The golden gene comes in at least two forms in people—light and dark. Europeans tend to have two light versions while everyone else has two dark ones. Having two copies of the light version of the golden gene is a big reason why many Europeans have lighter skin.
Here’s how part of the twin story probably unfolded. Both parents were of mixed heritage which means they each probably carried one copy of the light version and one copy of the dark version. The darker twin received a dark copy of the golden gene from each parent and so ended up darker than her parents. The lighter twin received a light version of the golden gene from each parent. So she was lighter than her parents.
All is not Golden
Of course, the golden gene does not explain everything. Japanese and indigenous Australians both have two dark versions of the golden gene. And Swedes and Italians both have two light versions of the gene. So there is a whole lot more going on in skin color genetics than just the golden gene.
Think of the golden gene as the base color of a person. Two light versions means someone starts out lighter, two dark versions means that they will start out darker and one of each means that a person will start out in between.
The final skin color is more than just this base though. Other genes can add or subtract to give the final color. Scientists are trying to identify these other genes. When they do, we’ll have a better handle on how skin color works in people.
