The Science Behind Hair Colors – Genetics of Our Natural Hair Color

Hair color contributes significantly to our overall visual appearance and our personalities. Thus, hair color products offer us the option of having the hair color of our choice today. However, naturally, we are born with a certain hair color, which might be different from our friends, cousins, or even our family members. The fundamental factor in our body to determine our hair color is determined by the amount of a pigment called melanin in the hair.

Science Behind Hair Color

Eumelanin and pheomelanin are the two pigments that play a significant role in how hair colors. Interestingly, everyone has the pheomelanin pigment in their hair, which creates orange and red hair color. The levels of black or brown eumelanin determine how dark hair will be and what hair color is dominant. As one might expect, low concentrations of the eumelanin pigment will yield blonde hair, while high concentrations result in darker brown hair. People with natural red hair have much higher pheomelanin levels in their hair than people with more common hair colors like brown, blonde, and black. To have a simpler understanding, here is a chart.

Basic Hair Colors – As Per The Type and Amount of Melanin Pigments

Black: Large amount of Eumelanin
Brown: Moderate amount of Eumelanin
Blond: Very little Eumelanin
Red: Mostly Pheomelanin with a little Eumelanin

What determines the Amount of Melanin Pigments in our Hair?

The science of our color can be explained by a little bit of physics and a lot of biology and chemistry. While the absorption and reflection of light also determine the hair color, the primary factor to determine our basic hair color is by our Genes. As mentioned above, the type and amount of melanin pigments in our hair gives a color. The total amount of melanin and the ratio between eumelanin and pheomelanin is unique to us and entirely determined by our genes. It is what gives you your natural hair color. However, it is not just a single or a couple of them, interestingly, several genes are involved in melanin production, and that can, therefore, affect our hair color. These genes switch on and off at different points in our lives – hence the reason our hair changes color as we get older.

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The Genetics of Our Natural Hair color

MC1R is the best-studied hair color gene in humans. Melanins are pigments derived from an amino acid called tyrosine. The color of the hair depends on the amount and type of melanin produced by melanocytes. Melanocortin 1 Receptor (MC1R) is the gene responsible for hair color determination. They found on the surface of melanocytes and also in other cells and play a role in the immune function in humans. There are three types of natural melanin.

  • Eumelanin

When MC1R is in the active condition, it produces eumelanin, which causes dark hair. It is also responsible for the protection of skin from damage by ultraviolet radiation.

  • Pheomelanin

When MC1R is in an inactive condition, the melanocytes will produce pheomelanin, which causes light or red hair. This pigment lacks the feature of protecting the skin from sunlight.

  • Neuromelanin

Since it is found in dopamine neurons, it colors some areas of the brain, which has no direct relation with hair color. Mutation of neuromelanin may result in a neurodegenerative disorder, which has an indirect relation with hair color.

Melanocortin 1 Receptor (MC1R)

Melanocortin 1 Receptor gene provides instructions for making a protein called the melanocortin 1 receptor, which is involved in the pathway that produces melanin. As the melanocortin 1 receptor controls which type of melanin is produced by melanocytes. When the receptor is turned on (activated), it triggers a series of chemical reactions inside melanocytes that stimulate these cells to make eumelanin. If the receptor is not activated or is blocked, melanocytes make pheomelanin instead of eumelanin. Many other genes also help to regulate this process. Most people have two functioning copies of the MC1R gene, one inherited from each parent. These individuals have black or brown hair because of the high amount of eumelanin. It is estimated that more than 90 percent of people in the world have brown or black hair.

Some people have variations in one copy of the MC1R gene in each cell that causes the gene to be turned off (deactivated). This type of genetic change is described as loss-of-function. For these individuals, eumelanin production is lower, while pheomelanin production is higher, so they have strawberry blond, auburn, or red hair. In an even smaller percentage of people, both copies of the MC1R gene in each cell have loss-of-function changes, and the melanin-production pathway produces only the pheomelanin pigment. The hair of these individuals is almost always very red. Even when the melanin-production pathway is making eumelanin, changes in other genes can reduce the amount of eumelanin produced. These changes lead to blond hair.

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Hair color ranges across a wide spectrum of hues, from flaxen blond to coal black. Many genes other than MC1R play a role in determining shades of hair color by controlling levels of eumelanin and pheomelanin. Some of these genes, including ASIP, DTNBP1, GPR143, HPS3, KITLG, MLPH, MYO5A, MYO7A, OCA2, SLC45A2, SLC24A5, TYRP1, TYR, ERCC6, GNAS, HERC2, IRF4, OBSCN, SLC24A4, TPCN2, and MITF, are involved in the production of melanin in the hair. Some of these genes are associated with gene transcription (which is the first step in protein production), DNA repair, the transport of substances (such as calcium) across cell membranes, or the structure of hair follicles. Several of these genes contribute to eye and skin color, but the exact role they play in determining hair color is unknown.

Hair color may change over time. Particularly in people of European descent, light hair color may darken as individuals grow older. For example, blond-haired children often have darker hair by the time they are teenagers. Researchers speculate that certain hair-pigment proteins are activated as children grow older, perhaps in response to hormonal changes that occur near puberty. Almost everyone’s hair will begin to turn gray as they age, although when it happens and to what extent is variable. Gray hair is partly hereditary and may vary by ethnic origin; it is also somewhat dependent on external factors such as stress. Hair becomes gray when the hair follicle loses its ability to make melanin, but exactly why that occurs is not clear. (Source)

The Genes Liable For Five Basic Hair Colors

Predominantly, human hair can be of five different colors: black, brown, blond, white/gray, and rarely Red. Among these major colors, different shades also exist. There is an interesting genetic science behind the particular color of our hair.

White/Grey Hair Color

Having white/grey hair color is basically due to the lack (or low amount) of either of the two melanin.

Black Hair Color

Black is the commonly seen hair color in Asia and Africa due to the fact that the people in these regions tend to have lower levels of tyrosinase in their bodies. Black eumelanin secretion causes the hair to turn black, which indicates that the MC1R is in the active state.

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Brown Hair Color

Human hair in brown color is seen in many shades like brown-ebony, brown-mahogany, brown-oak, etc. These many shades of brown are due to the presence of an allele, a specific variation in the gene that is found at the specific spot on the chromosome. For example, people with brown-ebony shaded hair have some alleles that catalyze the enzymes to produce a large amount of brown pigment. Some alleles in people with brown-Swedish blond suppress the enzyme production, which in turn causes less production of brown pigment. Based on this allele-enzyme activity, the shade of brown hair color differs.

Blond Hair Color

Blond hair is formed when there is a presence of a lower quantity of brown eumelanin with the absence of other pigments. People with blond hair color are mostly seen in European countries. The genome-wide association studies (GWAS) have found that the mutant gene that is responsible for blondness in the Northern European population is KIT ligand (KITLG), which has the ability to fight skin cancer. The KIT ligand is responsible for the mutation of skin color, blood stem cells, and sperm. Genes involved in the pigment production contain single-nucleotide polymorphisms (SNP) or the adenine guanine nucleotide, which alters the amount of KITLG present in the hair follicle. The mutation of the SNP or adenine-guanine nucleotide has been marked as a potential element of the blond hair phenotype.

Red Hair Color

The red hair color is very rare around the world. They are found in Northern Europe, specifically in Britain and Ireland. The gene present in red hair is recessive. The red color is caused by a series of mutations in the MC1R gene, which transmits to the hair more pheomelanin; this also results in pale skin. The arrangement of amino acids in the protein for red-haired people differs from that in people having other color hair. Red-haired people suffer a lot due to a higher risk of sunburns and skin cancer since the pheomelanin does not protect the skin from sunlight. People with red hair genes are more prone to skin cancer.

In Conclusion

The ultraviolet radiation from sunlight instantly triggers the MC1R gene to get mutated and also increases the stage of mutation in the tumor. Scientists have found that people with two MC1R alleles are more likely to have melanoma than those with one MC1R variant gene. The variant MC1R gene has decreased the synthesis of dopamine neurotransmitters in the brain. Thus red-haired people require a larger amount of anesthetic and are very conscious of thermal pain.

Also, Read – Why Do People Have Different Skin Colors?

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