Where is blonde hair originate from

Instead, in people of European ancestry, it causes blond hair through a 20 percent "turn of the thermostat dial" that regulates a signaling gene in the hair follicles of the skin. Elsewhere in the body, that signaling gene is involved in the formation of blood, egg, sperm, and stem cells.

Turning such a gene entirely on or off could be devastating. But a tiny mutation that tweaks the gene's activity in only one area—in this case the skin—allows for harmless changes, he said. Pardis Sabeti , a computational biologist at Harvard University and Broad Institute who was not involved in the research, said the study is a "beautiful demonstration" of this kind of tweaking, which has previously been poorly understood.

To find a single letter change and prove that it is a big driver of blond hair is a major scientific accomplishment, she said. To find the blond-hair gene mutation, Kingsley and his team looked at an area of the genome previously linked to blondness in people from Iceland and the Netherlands. They painstakingly identified the exact letter change that gives a person blond hair. The researchers tested what that letter change did in human skin cells grown in a petri dish.

The cells showed a reduction in activity in the switch that controls the signaling gene. Then Kingley's group bred lines of mice that either had the mutation or didn't have it.

The single-letter change didn't create blond mice, but those with the mutation had coats of a lighter color than those without. Learning the mechanism behind something as common—and as universally recognizable—as hair color, can help explain how genes work in other contexts, such as illnesses, where the stakes are higher, Kingsley said.

Hopi Hoekstra , a professor of genetics at Harvard who was not involved in the research, said the new finding confirms what researchers had long suspected: that small changes in gene expression caused by only a single DNA base pair change can lead to major changes in traits. Hair color "is a great starting point to do this type of molecular dissection" because it's simple to see whether the mutation results in a change in appearance, she said.

The blond hair mutation—or variant—is not genetically linked to any other traits, even eye color, Kingsley said, showing that none of our stereotypes about blonds are true. In contrast, many other human variants, such as some that cause red hair , are known to affect the protein structure of genes, and therefore trigger changes everywhere in the body the gene is expressed. Red hair, fair skin, and lighter eyes tend to travel as a package, he said, and may even be genetically paired with greater sensitivity to pain and temperature changes—though probably not fiery tempers.

Additional photos are available here. Myles worked with Bustamante, who was also at Cornell, to design the study. Then back in the islands, Myles and Timpson went village to village explaining what they wanted to do and asking for permission to gather data, Myles speaking in Solomon Islands pidgin, the most widely understood language. When the local chief gave the OK, the researchers recruited participants and assessed hair and skin color using a light reflectance meter, took blood pressure readings and measured heights and weights.

They asked the villagers to spit into small tubes to provide saliva to be used for DNA extraction. In the span of a month they collected more than 1, samples. For instance, simply finding a level spot for the scale to weigh study participants was a challenge. Soon after, Kenny joined the lab and started the analysis, selecting 43 blond- and 42 dark-haired Solomon Islanders from the opposite 10 percent extremes of the hair pigmentation range.

She used these in a genome-wide association study, a method to reveal differences in the frequency of genetic variants between two groups, that usually requires thousands of samples. Because the vast majority of human physical characteristics analyzed to date have many genetic and environmental factors, Kenny expected an inconclusive result that would require much further study.

The team went on to identify the gene responsible, TYRP1 , which encodes tyrosinase-related protein 1, an enzyme previously recognized as influencing pigmentation in mice and humans.

Further research revealed that the particular variant responsible for blond hair in the Solomon Islands is absent in the genomes of Europeans. That something could be due to some advantage of having blonde hair or simple luck. If blonde hair had an advantage, then blondes would have more kids than darker haired people. Over time, their numbers would increase. Alternatively it could be that one of the founding members of the islands happened to have the blonde mutation.

Or maybe some catastrophe struck where there were only a few survivors, one of whom happened to have the mutation. When the island was repopulated from these survivors, blondes would be much more common than before the catastrophe. In both cases, blondes would make up a significant part of the population even without an advantage. So there you have it. All blondes do not share the same blonde ancestor. Blonde hair has appeared at different times and in different ways.

By Dr. Barry Starr, Stanford University. One theory for how hair color works Traits spreading through a population Why redheads and blondes aren't going to be dying out anytime soon. Unlike blue eyed people, not all blondes have the same ancestor.

DNA has the instructions for hair color. New traits often appear because of mutation. The Tech Interactive S. Market St. San Jose, CA The Tech is a registered c 3. Federal ID Its content is solely the responsibility of the authors and does not necessarily represent the official views of Stanford University or the Department of Genetics.

The Tech Interactive. Hair Color.