![]() ![]() Human hair pigmentation-biological aspects. Molecular genetics of human pigmentation diversity. Association of five SNPs with human hair colour in the Polish population. Siewierska-Górska A, Sitek A, Żądzińska E, Bartosz G, Strapagiel D. The melanocortin-1 receptor: red hair and beyond. Diversity of human hair pigmentation as studied by chemical analysis of eumelanin and pheomelanin. Free full-text available from PubMed Central: PMC2367449. A genome-wide association study identifies novel alleles associated with hair color and skin pigmentation. Han J, Kraft P, Nan H, Guo Q, Chen C, Qureshi A, Hankinson SE, Hu FB, Duffy DL, Zhao ZZ, Martin NG, Montgomery GW, Hayward NK, Thomas G, Hoover RN, Chanock S, Hunter DJ. Absence of TRP-2 in melanogenic melanocytes of human hair. Free full-text available from PubMed Central: PMC3057002.Ĭommo S, Gaillard O, Thibaut S, Bernard BA. Model-based prediction of human hair color using DNA variants. Scientific journal articles for further readingīranicki W, Liu F, van Duijn K, Draus-Barini J, Pośpiech E, Walsh S, Kupiec T, Wojas-Pelc A, Kayser M. Hair becomes gray when the hair follicle loses its ability to make melanin, but exactly why that occurs is not clear. Gray hair is partly hereditary and may vary by ethnic origin it is also somewhat dependent on external factors such as stress. Almost everyone’s hair will begin to turn gray as they age, although when it happens and to what extent is variable. Researchers speculate that certain hair-pigment proteins are activated as children grow older, perhaps in response to hormonal changes that occur near puberty. For example, blond-haired children often have darker hair by the time they are teenagers. Particularly in people of European descent, light hair color may darken as individuals grow older. Several of these genes contribute to eye and skin color, but the exact role they play in determining hair color is unknown. 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. 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 hair. Many genes other than MC1R play a role in determining shades of hair color by controlling levels of eumelanin and pheomelanin. Hair color ranges across a wide spectrum of hues, from flaxen blond to coal black. Even when the melanin-production pathway is making eumelanin, changes in other genes can reduce the amount of eumelanin produced. The hair of these individuals is almost always very red. 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. For these individuals, eumelanin production is lower, while pheomelanin production is higher, so they have strawberry blond, auburn, or red hair. This type of genetic change is described as loss-of-function. Some people have variations in one copy of the MC1R gene in each cell that causes the gene to be turned off (deactivated). It is estimated that more than 90 percent of people in the world have brown or black hair. These individuals have black or brown hair, because of the high amount of eumelanin. Most people have two functioning copies of the MC1R gene, one inherited from each parent. Many other genes also help to regulate this process. If the receptor is not activated or is blocked, melanocytes make pheomelanin instead of eumelanin. When the receptor is turned on (activated), it triggers a series of chemical reactions inside melanocytes that stimulate these cells to make eumelanin. The melanocortin 1 receptor controls which type of melanin is produced by melanocytes. This gene provides instructions for making a protein called the melanocortin 1 receptor, which is involved in the pathway that produces melanin. The best-studied hair-color gene in humans is called MC1R. The type and amount of melanin in hair is determined by many genes, although little is known about most of them. ![]() Mostly pheomelanin with a little eumelanin The type and amount of melanin determines hair color An abundance of another pigment, called pheomelanin, gives people red hair. ![]() An abundance of one type of melanin, called eumelanin, gives people black or brown hair. Hair color is determined by the amount of a pigment called melanin in hair. ![]()
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