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.
BROWNISH RED HAIR SERIES
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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