National Geographic News
Photo of a young boy with curly blond hair.

A new study that found blond hair is the result of a small genetic "tweak" could provide clues for how to genetically treat illnesses.

Photograph by Martin Schoeller, National Geographic Creative

Karen Weintraub

for National Geographic News

PUBLISHED JUNE 1, 2014

For thousands of years, people have both prized and mocked blond hair. Now, a new study shows that many can thank a tiny genetic mutationa single letter change from an A to a G among the 3 billion letters in the book of human DNAfor their golden locks.

The mutation "is the biological mechanism that helps create that [blond] color naturally," said David Kingsley, a professor of developmental biology at Stanford University and a Howard Hughes Medical Institute investigator, who led the research. "This is a great biological example of how traits can be controlled, and what a superficial difference blond hair color really is."

Kingsley, a brunet, said the study, published today in Nature Genetics, also offers a powerful insight into the workings of the human genome. The mutation doesn't alter the protein production of any of the 20,000 genes in the human genome, he said. 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.

 

Photo of a young girl with blond hair.
Blond hair, like this young girl's, is caused by a single DNA base pair change.
Photograph by Martin Schoeller, National Geographic Creative

 

A Subtle Change With Big Results

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. "Understanding these principles will help people ... trying to find drugs for diseases."

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. "But it highlights how difficult this is going to be for more complex human traits, like mental illness, which we've never been very good at measuring."

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.

26 comments
Grace Takelal
Grace Takelal

My Son is  of three races , as a baby until puberty , his hair was blond with loose curls at the bottom and sides .His skin was that of a medium tanned white persons . Once puberty started , his skin got a deeper tan shade ,and his hair color changed to a dark sandy reddish brown ,and curls got  wavier  .Now that he is  a grown up ,his hair is the same except before it turns white .  Then :It goes from Dark Brown to red to blond before white or grey . His beard and Goatee  are  also the same color but the sides are always blond only before they turn white . It has been amazing to watch the changes  and others reactions to him before and after .

Tracy Green
Tracy Green

I knew i would find info on red heads it is at the end and i know red hair makes changes all over the body like getting to much sun causes my freckles to turn avacado and my hair to become streaked with gold

Csimensis .
Csimensis .

I am black, but the hair on my arms and some of the hair on the front of my head is blonde. My grandfather used to have a full head of blonde hair when he was a child, and I get it from him. My family has lots of Northern and Western European influence, and we think this is the reason many of us have blondish hair.

J. Griffin
J. Griffin

I was born with straight jet black hair. Now I have curly reddish-brown hair with golden highlights.  Hopefully they will do a study on why hair color and texture can change over time.

Robin Monroe
Robin Monroe

I am a Norwegian American woman, 55 years old. Never had a child. Born blonde, and I've been blonde all my life. My hair was platinum blonde as a very young child and changed to a more yellow/wheat color when I reached about the 3rd grade.   My mother was born blonde, and she stayed blonde until just after her first child was born and then her hair turned a light ash brown. 

William Lanteigne
William Lanteigne

I was born blonde, but by the 6th grade my hair was "ash blonde." By the 8th grade it was medium-brown, by graduation dark brown, but my beard was distinctly auburn. I'm coming full circle, as my hair is now beginning to become silver.

Rebekah Lamb
Rebekah Lamb

You do know that science will never be allowed to cure or stop most most illness'. Because treating sickness is a BIG MONEY BUSINESS. Just like War. Sorry all us little people. We suffer they make MONEY. 

Luba R.
Luba R.

i was born blonde, but after reaching 35 my hair changed to dark;;;light to medium brown. How this can be explained then?


Berty Popperdopper
Berty Popperdopper

I guess this just proves that we are all the same :-)

Even if i am opposed to burning people alive for being bad juju wizards. We are all Africans, no matter the colour of our skin.

Leo Kretzner
Leo Kretzner

Okay, the change is in the regulatory region of KITLG, the KIT ligand - ie, a smallish protein that binds to the receptor called KIT. When KITLG binds to KIT the latter starts actively signalling to the interior of the cell.  These genes are also crucial for blood cell development and other effects.


Interestingly, another mutation in this gene is associated with Progressive Familial Hyperpigmentation, with darkly pigmented areas of skin.

Leo Kretzner
Leo Kretzner

Well it would be nice to know WHAT gene the mutation is in! I'd think most readers of Nat Geo are smart enough to take that information in (or ignore it). From what's said I'm thinking it's a gene for a receptor, but I guess I'll have to read elsewhere for that.

Prem Janardhan
Prem Janardhan

There are three billion base pairs in the human genome as per Wikipedia - is that wrong?

Eo Raptor
Eo Raptor

"... a single letter change from an A to a G among the 3 billion letters in the book of human DNA..."


I am reading a National Geographic site, yes? Three billion <u>letters</> in human DNA? I believe that's off by nearly six orders of magnitude. Indeed, I don't know that there's three billion of ANYTHING related to human DNA; except maybe the possible combination of genes along the 23 pairs of chromosomes. 


I think an editor needs retiring. 

robert brooke
robert brooke

In the Aborigines of Australia,blond hair is not uncommon in children.Is the same gene gene involved?

Mona Torgersen
Mona Torgersen

@Robin Monroe I'm from Norway, and I was born blonde, but it also got darker as I got older. Now my natural hair colour is a mousy light brown. My dad was a strawberry blonde and my mother had dark brown hair.

Josh Tatro
Josh Tatro

@Luba R. That question is akin to asking why one's hair goes gray/white upon reaching late adulthood. The answer is simple (kind of): changes in the way your body produces hormones (or doesn't) affects the natural production of pigment, among other things. As for why it changed during your early to mid 30's, my first guess would be that you had children during or immediately prior to that point in your life. The hormonal changes associated with pregnancy are well known to cause many physiological changes in women, and blond (or lighter colored hair in general) changing to darker shades or to brown is very common. But, even if you didn't have kids, it's still not at all unusual for hair color to change along with hormones, which likewise influence the production/distribution of pigment; in fact, most children born with blond hair see it change pretty consistently throughout their lives until they are ostensibly no longer blond by adulthood. Pregnancy merely speeds up this process.

Eo Raptor
Eo Raptor

@Prem Janardhan


No. The problem is that, in my understanding (as often wrong as right) is that the word "letter," in this context refers to the individual nucleotides, not the base pairs. There are only four nucleotides: Adenine, Guanine, Cytosine, and Thymine (or Uracil, if you are talking about RNA).


I apologize, however (regardless of whether I'm right, or wrong), for making the personal remark about the editor. It was uncalled for, and in bad taste. 


Experts, out there, please let me know if I'm using the concept of "letter" incorrectly.

Gorman Ghaste
Gorman Ghaste

@Eo Raptor The human genome contains approximately 3 billion base pairs, which reside in the 23 pairs of chromosomes within the nucleus of all our cells. Each chromosome contains hundreds to thousands of genes, which carry the instructions for making proteins. Each of the estimated 30,000 genes in the human genome makes an average of three proteins.

Phil Petersen
Phil Petersen

@robert brooke  In the Solomon Islands on the island of Malaita many people are born with blonde hair. This changes to ginger as they age

Prem Janardhan
Prem Janardhan

@robert brooke  Probably a different one, certainly there is blonde hair in Melanesia as well, due to a different mechanism.

Eo Raptor
Eo Raptor

@Gorman Ghaste @Eo Raptor


No argument with that. But, that's not what the article said -- unless the author is using an idiosyncratic meaning for "letter."

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