FAIR-HAIRED people have trouble learning the alphabet, if blond jokes are to be believed. Now scientists have tracked blondeness down to a single DNA “letter”.
US researchers say they have identified the DNA base-pair responsible for the classic blonde look of northern Europeans. Their study, published today in the journal Nature Genetics, resolves a genetic mystery over the causes of a human feature that has fascinated people for millennia.
“In some cultures (blond hair) is stigmatised as a ghostlike abnormality (or) sign of promiscuity. In contrast, fair hair was associated with youth and beauty in the earliest written works of ancient Greece,” the paper says.
“Despite thousands of years of interest, the molecular basis of common human hair colour phenotypes is still incompletely understood.”
Recent genomic studies have implicated eight genes in the blond hair of northern Europeans. Scientists want to pinpoint the exact mutations that cause the trait, to better understand human evolution and to improve genetic predictions.
The new study, led by researchers from Stanford University in California, focused on a particular gene known as KITLG. The researchers zeroed in on a region of the gene where a small variation in the DNA sequence — known as an SNP or “single nucleotide polymorphism” — has been found to influence the hair colour of people in Iceland and the Netherlands.
SNPs are caused by ‘typos’ in the DNA copying process when cells divide. They can involve errors in just one of the thousands of base-pairs in each gene.
When the team engineered the same mutation in the KITLG gene in mice embryos, they produced rodents with golden-brown fur. Mice without the mutations emerged with dark fur.
The results showed that a “single-base change” was enough to determine hair colour, the researchers found.
The study suggests that a similar approach — combining animal studies with genomics studies and large-scale human surveys — could pinpoint the DNA changes responsible for other human traits such as eye colour, susceptibility to disease and response to drugs.