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In the gene combination with the dominant coat color gene B , black eumelanin is formed.
In the gene combination with the recessive coat color gene b , if it is homozygous , genotype bb, chocolate-brown eumelanin is formed. For both forms of eumelanin, the allele E must be present at least once on the extension locus .

The eumelanin is a pigment , which together with a second type of pigment, the phaeomelanin , the hair and skin color determined. The pigments are also called melanins . Eumelanin dominates in brown and black hair, while the second type of melanin, pheomelanin, as a red pigment, is responsible for light blonde, blonde and red hair. Gray hair occurs when melanin production decreases with age. The melanin is then increasingly replaced by the accumulation of air bubbles in the hair shaft . The hair appears gray to white.

If the hair is gray, either conventional dyes can be used for tinting or coloring, or repigmentation through the use of dyes that are only gradually activated by the natural oxygen in the air and instead of the missing melanin ensure a gradual repigmentation of the hair.


Tyrosine is biosynthetically converted in the first step with tyrosinase to DOPA and then to Dopaquinone . In the next conversion step of the metabolic pathway, the dopachinone is processed further to 5,6- indolquinone , which is then polymerized to eumelanin . If, due to a genetic lack of an enzyme, for example because of the homozygous presence of the allele e on the extension locus, the conversion step from dopachinone to 5,6-indolquinone cannot take place, only pheomelanin is formed.

Biosynthesis of eumelanin and pheomelanin


Individual evidence

  1. James J. Nordlund, Raymond E. Boissy, Vincent J. Hearing, William Oetting, Richard A. King, Jean-Paul Ortonne: The pigmentary system: physiology and pathophysiology. Wiley-Blackwell, 2006, ISBN 1-4051-2034-7 .
  2. Pascal Kintz: Drug testing in hair. CRC Press, 1996, ISBN 0-8493-8112-6 , p. 74.