-- Mary Elizabeth Dallas
THURSDAY, May 3 (HealthDay News) -- All blonds are not alike,
according to a new study that finds different genes dictate flaxen
locks in different areas of the globe.
The genetic variant that causes many dark-skinned people from
the Solomon Islands to have blond hair is different from the gene
possessed by blond Europeans, the study found. Researchers from
Stanford University School of Medicine found that this particular
variant is absent in the genomes of Europeans.
"Since most studies in human genetics only include participants of European descent, we may be getting a very biased view of which genes and mutations influence the traits we investigate," study co-senior author Carlos Bustamante, professor of genetics at Stanford, said in a university news release. "Here, we sought to test whether one of the most striking human traits, blond hair, had the same -- or different -- genetic underpinning in different human populations."
The frequency of blond hair in the Solomon Islands is between 5
percent and 10 percent, the researchers said.
"They have this very dark skin and bright blond hair," study co-senior author Sean Myles, a former Stanford postdoctoral scholar who is now an assistant professor at the Nova Scotia Agricultural College, said in the release. "It was mind-blowing. As a geneticist on the beach watching the kids playing, you count up the frequency of kids with blond hair, and say, 'Wow, it's 5 to 10 percent.'"
Many locals assumed their blond hair was the result of sun
exposure or high fish consumption. Others believed it was a trait
passed on by European explorers. The study authors, however, sought
to determine if there was a unique genetic basis for this
In conducting the study, which is scheduled to be published in
the May 4 issue of
Science, the researchers assessed Islanders' hair and skin color using a light reflectance meter. The investigators also took participants' blood pressure, measured their heights and weights, and collected 1,000 saliva samples from the villagers to examine their DNA.
To look for the genes associated with blond hair, the
researchers then selected 43 of the most blond and 42 of the
darkest-haired Islanders from the samples collected, and looked for
differences in the frequency of genetic variants between the two
The researchers immediately identified a single signal on
chromosome 9, which accounted for 50 percent of the variance in the
participants' blond hair. They later identified the gene
responsible, called TYRP1. The authors noted that the genetic
variant that leads to blond hair among people in the Solomon
Islands is not found in the genomes of Europeans.
"Within a week we had our initial result," the study's co-first author, Eimear Kenny, said in the news release. "It was such a striking signal pointing to a single gene -- a result you could hang your hat on. That rarely happens in science. It was one of the best experiences of my career."
"The human characteristic of blond hair arose independently in equatorial Oceania," she said. "That's quite unexpected and fascinating."
"This is one of the most beautiful examples to date of the mapping of a simple genetic trait in humans," David Reich, a professor of genetics at Harvard University who was not involved in the study, said in the news release.
The study authors said the finding underscores the need for
genetic studies on isolated populations.
"If we're going to be designing the next generation of medical treatments using genetic information and we don't have a really broad spectrum of populations included, you could disproportionately benefit some populations and harm others," Bustamante said.
The U.S. National Human Genome Research Institute has more about
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