Researchers identified a small genetic change that can mean the difference between blonde or brown hair.
Scientists found that replacing one of four DNA letters in a certain spot in the genome was the key to lighter hair, AAAS Science reported.
"It really is a nice story that pulls together and helps make sense of a lot of the biology that we have partially understood up to this point," Richard Sturm, a molecular geneticist at the University of Queensland in Brisbane, Australia, who was not involved with the work, said in the AAAS report.
Over the past six years researchers have linked at least eight DNA regions to fair hair based on a certain letter that is not seen in people of other hair colors.
These base changes, called single-nucleotide polymorphisms (SNPs), were often found in genes dealing with pigment production. Mutations in these genes have been known to affect skin and hair color.
In Northern Europeans the SNP closest-linked to blondness was called KITLG, which codes for a protein that is key to making sure cells go to their proper places in the body and specialize accordingly, the news release reported.
David Kingsley, an evolutionary geneticist at Stanford University in California, found the gene altered the coloration of fish called sticklebacks.
"We had a choice," Kingsley said. "We could study skin color in fish or in humans-it was the very same problem in the very same gene."
Researchers created two variations of the KITGL gene to be put into mice; in one the blonde-generating SNP was left intact while in the other it was switched to another base. The mice with the blonde-generating SNP proved to be lighter than those without it.
"This study provides solid evidence" that this switch regulates the expression of KITLG in developing hair follicles," Fan Liu, a genetic epidemiologist at Erasmus MC in Rotterdam, the Netherlands, who was not involved with the work, said in the news release.
