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Secret of Scandinavian blondes revealed

Prince Sigismund Casimir Vasa of Poland was blonde as a child, but his hair darkened in later years.
Wikicommons/Portrait painted by Peter Danckerts de Rij (1605–1661)

Once thought of as a “junk” DNA, a single “one-letter mutation,” is all it takes to make a blonde a blonde or a brunette a brunette,” according to Stanford University Medical Institute investigator David Kingsley who discovered that all it takes to determine the true hair color of an individual is a “single change, from an ‘A’ to a ‘G’ in the four-letter DNA code of the Kit ligand gene (already associated with hair color, but not in determining hair growth.). The specificity of the switch shows exactly how independent color changes can be encoded to produce specific traits in humans."

He also explained that the while Kit ligand gene “not only aids the development of pigment-producing cells, but has a host of other roles around the body, including influencing behavior of blood stem cells, sperm or egg precursors, and gut neurons, this newly uncovered mutation doesn’t seem to do anything else other than make a blonde a blonde, and is particularly prevalent in people from Scandinavia and Iceland. It doesn’t affect eye color or skin color or intelligence.”

Although many readers may think of this as little more than a new bit of trivia, Kingsley’s findings actually play a more important part than merely understanding why humans have such variations in skin, eye and hair coloring, it helps scientists learn more about how small alterations in “little-understood regions of the genome might affect disease and other traits.”