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The phenotypic color variation observed in the epidermis and hair of mammals is primarily determined by the levels of eumelanin and pheomelanin in the examined tissue. In an average human individual, eumelanin is more abundant in tissues requiring photoprotection, such as the epidermis and the retinal pigment epithelium. [4]
Pheomelanin colors hair orange and red. Eumelanin, which has two subtypes of black or brown, determines the darkness of the hair color; [4] more black eumelanin leads to blacker hair and more brown eumelanin to browner hair. [6] All human hair has some amount of both pigments. [9] Over 95% of melanin content in black and brown hair is eumelanin ...
The melanocortin 1 receptor (MC1R) gene is primarily responsible for determining whether pheomelanin and eumelanin are produced in the human body. Research shows at least 10 differences in MC1R between African and chimpanzee samples and that the gene has probably undergone a strong positive selection (a selective sweep ) in early Hominins ...
There are also differences in the quantity and relative amounts of eumelanin and pheomelanin. [13] Pigmentation including tanning is under hormonal control, including the MSH and ACTH peptides that are produced from the precursor proopiomelanocortin. Vitiligo is a skin disease where people lack melanin in certain areas in the skin.
The pigment pheomelanin gives red hair its distinctive color. Red hair has far more of the pigment pheomelanin than it has of the dark pigment eumelanin. The genetics of red hair appear to be associated with the melanocortin-1 receptor (MC1R), which is found on chromosome 16. In 1995, Valverde, et al. identified alleles on MC1R associated with ...
The gene variation's primary effect is to promote eumelanin synthesis at the expense of pheomelanin synthesis, although this contributes to very little variation in skin reflectance between different ethnic groups. [92] Melanocytes from light skin cells cocultured with keratinocytes give rise to a distribution pattern characteristic of light ...
Side effects may include sun sensitivity, skin redness, thickening, or itching. [6] Low concentrations may be used in cosmetics. [6] Kojic acid has been found to be an effective lightener in some studies and is also allowed to be used in cosmetics. [6] Side effects include redness and eczema. [6]
However, there are differences between the biology of melanophores and that of melanocytes. In addition to eumelanin, melanocytes can generate a yellow/red pigment called phaeomelanin. [citation needed] The purple-striped dottyback, Pseudochromis diadema, generates its violet stripe with an unusual type of chromatophore.