Unraveling the Secrets of European Color

New Genetic Study Finds DNA Differences Associated with Hair, Skin, and Eye Colors in Europeans

November 2, 2007

A new genetic study was just released in Nature Genetics that found six regions of DNA that are involved in the lighter eye, hair, and skin color of many Europeans. We are getting a bit closer to being able to figure out a European's coloration from just their DNA.

What the researchers did was to get descriptions of 2,986 Icelanders and to compare their DNA to each other using the following traits:

  • Red hair vs. no red hair
  • Blonde hair vs. brown hair
  • Blue eyes vs. brown eyes
  • Blue eyes vs. green eyes
  • Sun sensitive skin vs. less sun sensitive skin
  • Freckles vs. no freckles

The researchers did not look at all 6 billion letters of these Icelanders. Instead they looked to see which of around 300,000 DNA differences each group had in common and which ones they did not.

The researchers then followed up with an additional 2,718 Icelanders and a group of 1,214 Dutch people. From all of this, the researchers identified six DNA regions that were important for making Europeans lighter in color.

The 300,000 differences sounds like a lot of but it is a small part our DNA. What this means is that the differences they found may or may not have identified a certain gene. And almost certainly these differences were not the cause of the trait being studied but were instead just nearby.

This kind of study is not exhaustive and it will definitely miss some genes because the researchers couldn't look at all of the DNA. For example, we know they missed a key skin color gene— SLC24A5.

Basically this is an early study that can help identify regions of DNA that are important in human coloration. The data from this study can be used in future studies to focus on these regions to really figure out what is going on. The researchers went on to make educated guesses about which genes in the identified DNA regions are probably involved in skin, hair, and eye color.

Identified DNA Regions (and Possible Genes)

Studies have shown that our human ancestors most likely had dark hair, dark skin and brown eyes. The researchers looked for genes in the identified DNA regions that might cause lighter hair, skin or eyes.

Below is a list of the genes they concluded might play a role in human pigmentation. As was stated before, the researchers could not say whether these genes are really the key genes. They were selected as the most obvious candidates.

Also, many of the identified regions have a strong association with some traits and a weaker one with other traits. The researchers can't be sure if this is due to one gene having multiple effects. Or multiple genes each having a single effect.

MC1R: Scientists already know a lot about this gene (click here to learn more). Basically people can have different versions of this gene that can lead to fair skin and freckles. Having two copies* of a MC1R gene that is a certain version gives someone red hair along with the freckles and fair skin.

The researchers found no link between changes in the MC1R gene that lead to red hair and any particular eye color. They did find, however, that sometimes changes in this region did lead to blonde instead of brown hair. Because the researchers aren't really looking at the MC1R gene, they can't tell if the reason for this is MC1R or a different gene.

OCA2: The region that contains this gene was involved in many traits. OCA2 has long been known as a key gene in determining brown vs. blue and green eyes. However, it probably does not cause green eyes, it just allows for it to happen (click here to learn more). Here the researchers also discovered that the region that contains OCA2 is involved in determining blonde vs. brown hair as well.

SLC24A4: The region that contains this gene was key in determining green eyes vs. blue as well as blonde hair vs. brown.

TYR: The region that contains this gene was involved in a number of different traits. One version of the gene appears to lead to freckles without fair skin. A different version is involved in green vs. blue eyes although this was not as strong as with the SLC24A4 gene.

6p25.3 (Chromosome 6 region): This DNA region appears to contain a previously unidentified gene involved in freckles and fair skin. It may also be involved in giving brown hair instead of blonde.

KITLG: The region that contains this gene was important for distinguishing brown vs. blonde hair.

*We have two copies of most of our genes. And each of these genes comes in different versions. Most of the wonderful diversity around us comes from mixing and matching these different gene versions. The genes identified here are no different.

How Coloration Genes Work

Coloring happens because of pigments that are made in specialized cells called melanocytes. Genes control how many melanocytes we have and how much (and what kind of) pigment they make. Changes in any of the genes involved in these processes result in different coloration.

Let's look at MC1R as a classic example. The job of the MC1R gene is to create a protein that turns one pigment, pheomelanin, into a different pigment, eumelanin. Pheomelanin in the pigment that gives people red hair and eumelanin gives the other colors.

So when MC1R is working well, people do not have red hair because their pheomelanin has been turned into eumelanin. But if someone has two copies * of a version of MC1R that does not work well, he or she end up with a build up of pheomelanin. And red hair.

Other genes affect other aspects of coloration. Some like OCA2 are involved in making pigment. Some versions of OCA2 make lots of pigment and so someone has brown eyes. Other versions of OCA2 make very little pigment and so result in blue eyes.

Different combinations of different versions of the genes identified in this study lead to different amounts (and kinds) of pigments. And different trait combinations. So a redhead with freckles and brown hair has one set of versions of these genes. And a blue eyed, blonde haired European has a different set.…

To better understand what this all means, let's give a few examples and see if we can figure out what genes these folks might have. Remember, this is based on what we know right now. We may be missing a lot of genes that could be involved as well.

Red hair, fair skin, freckles, green eyes

Someone with this combination most certainly has two copies of the MC1R gene that lead to red hair, freckles, and fair skin. The green eyes mean that he or she has the not-brown-eye version of OCA2 and the green version of either SLC24A4 or TYR gene.

Brown hair, darker skin, freckles, and blue eyes

Someone with this set of traits most likely has the freckle version of the TYR gene. These folks tended to have darker hair and skin with freckles. The blue eyes almost certainly come from a certain version of the OCA2 gene. And probably a certain version of TYR or SLC24A4 that keeps green eyes away

Blonde hair, blue eyes, fair skin with no freckles

There are a number of possibilities here. It may be that this person has a certain version of OCA2 that causes all of these traits. Or it could be a combination of OCA2 and KITLG. Or OCA2 and SLC24A4.

The study done here has certainly taken a huge step in finding the DNA regions involved in the lighter color of many Europeans. The next step will be to look harder at these regions to confirm which genes are really involved. And to look at more DNA differences to find DNA regions they may have missed. Perhaps soon scientists will be able to generate a picture of a crime suspect with just the DNA he or she left behind!

*We have two copies of most of our genes. And each of these genes comes in different versions. Most of the wonderful diversity around us comes from mixing and matching these different gene versions. The genes identified here are no different.

Pigments are made in
melanocytes like this one.