Blonde or brunette: Single DNA letter change determines hair color


Men and women who enjoy the perks of being naturally blonde have something in their genes that they have to be thankful for. A new study reveals that one simple difference in the genetic code is responsible for why some people have blonde hair.

In the new study "A molecular basis for classic blond hair color in Europeans" which was published in the Nature Genetics on June 1, David Kingsley, from the Howard Hughes Medical Institute of the Stanford University School of Medicine in California, and colleagues, found that switching just one "letter" of the DNA can turn brunettes into blondes .

Kingsley, an evolutionary geneticist, has been studying a fish known as the three-spined stickleback to understand evolution and in the process discovered a gene that has an effect on the color of the fishes. For their new study, Kingsley and his colleagues conducted an experiment on mice to see if the gene has the same effect in other species. They found that the so-called "blonde" switch changes the activity of the gene called Kit ligand and results in mice to be born with light and golden brown fur.

"Mice carrying ancestral or derived variants of the human KITLG enhancer exhibit significant differences in hair pigmentation, confirming that altered regulation of an essential growth factor contributes to the classic blond hair phenotype found in northern Europeans," Kingsley and his colleagues wrote.

A closer look at human cells grown in the laboratory also revealed that the blond-generating single nucleotide polymorphism or SNP, the single letter change in the DNA, reduced Kit ligand activity by about 20 percent but it was enough to change the color of the hair.

The researchers also found that such change does not have any effect on the brain at all dispelling myths that people with blonde hair tend to have lower IQ. They also found that hair color is not genetically associated with eye color.

"This particular genetic variation in humans is associated with blond hair, but it isn't associated with eye color or other pigmentation traits," Kingsley said. "The specificity of the switch shows exactly how independent color changes can be encoded to produce specific traits in humans."

Kingsley said that the mechanism that controls hair color does not change the biology of other parts of the body proving that hair color is one of the human traits that can be truly considered as skin deep.

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