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Hair Color: Blond Hair

Hair pigmentation, similar to skin pigmentation, is mainly determined by the amount and distribution of melanin. Specifically, two types of melanin, eumelanin (of brown-black tones) and pheomelanin (of all yellow and/or reddish tones).

Thus, in general, the more melanin is present, the more intense the dark color of the hair.

Natural hair colors

The natural hair color is black, brown, blond, and red.

Hair color is genetically associated with skin color and eye color.

Black hair color is the most common. Blond and red hair is most often associated with diseases such as skin cancer and genetic characteristics such as albinism.

Genetics and biochemistry of hair color

As mentioned at the beginning, there are two types of melanin, eumelanin, and pheomelanin. The amount of melanin is directly proportional to the intensity of hair color, analogous to what happens with the skin.

For example, a low concentration of brown eumelanin in the hair will make it blond, while more brown eumelanin will give it a brown color (also much more black eumelanin will result in black hair and a low concentration of black eumelanin in the hair will make it gray).

All humans have pheomelanin in their hair. Pheomelanin is more chemically stable than black eumelanin but less chemically stable than brown eumelanin, which degrades more slowly when oxidized. Therefore, bleach causes dark hair to turn reddish-brown during the artificial dyeing process. As the pheomelanin continues to degrade, the hair gradually turns orange, then yellow, and finally white.

Until relatively recently, not much was known about the genes that control melanin production and, by extension, are involved in determining hair color. However, we now know that there are more than 23 genes involved in determining hair color. These genes are as follows: MC1R, TYR, OCA2, SLC24A5, MATP AND ASIP, DTNBP1, GPR143, HPS3, KITGL, MLPH, MYO5A, MYO7A, SLC45A2, TYRP1, ERCC6, GNAS, HERC2, IRF4, OBSCN, SKC24A5, TPNC2, and MITF, all of which are related to melanin formation and distribution processes.

A practical example that highlights the number of genes involved in the formation and the great genetic variability that can produce so many variants and the relationships established between the different alleles can be found in the wide range of hair present in the human species.

Blond hair color

In the case of blonde hair color, thanks to recent studies carried out by scientists at Stanford and Georgia universities, we know that its appearance may be determined by the presence of a single mutation in the KITLG gene, an essential gene involved in the migration, proliferation, and survival of many cell types.

Gene or region studied

  • TPCN2
  • 12q21.33
  • HERC2
  • 14q32.12
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