A condition characterized by the complete lack of pigments (or melanin)
Melanin is a compound that is responsible for the color of the skin, hair, feathers, scales, etc. It is produced in plants, animals, and protists. It is produced within the specialized cells called melanocytes, particularly in specialized organelles called melanosomes. Melanin is derived from the amino acid tyrosine and the production of melanin is referred to as melanogenesis. Melanin is produced by catalyzing tyrosine through the enzyme, tyrosinase. It is important in living organisms since it renders protection against the adverse effects of light exposure. It is capable of absorbing the sun’s UV rays. This is important because without melanin, the sun’s UV rays may damage DNA especially when exposed to sunlight for a longer period. The complete absence of pigmentation due to lack of melanin production is termed amelanism. Hypomelanism is a condition where there is only a partial lack of pigmentation. In contrast, an accentuated pigment production characterizes hypermelanism. Amelanism occurs in animals like in fish, amphibians, reptiles, birds, and mammals. Despite the lack in melanin pigments, animals with amelanism can still have red or yellow spots due to chromatophores that produce non-melanin pigments. It can also occur in humans as albinism (particularly the oculocutaneous type).
Word origin: a- (absence) + melanism