Hair colour is genetically programmed and established in-utero.
Pigmentation is due to the presence of Melanin a water-insoluble polymer of compounds derived from the amino acid Tyrosine which is located within the Melanocytes.
Melanosynthesis may produce:
– formed by the reaction of the enzyme tyrosinase with the amino acid tyrosine. It produces hair colours varying between reddish brown – black.
– formed by the reaction of the enzyme tyrosinase with the amino acids tyrosine and the sulphur rich cysteine. This produces hair colours varying from yellow(blonde) to red (titians).
Variations in pigmentation relate to the number, size and distribution of Melanosomes (single melanin containing organelles) within the Melanocytes. These are specialised skin cells producing melanin and having branches (Dentrites) located within hair follicles through which tiny pigment granules are injected into the keratinocytes during hairshaft genesis.
Melanin affords some skin protection by absorbing ultraviolet radiation.
Tyrosinase inactivity > nil melanogenesis = possible Albinism.