Albinism is a disorder caused by

Albinism is a genetic condition in which the body cannot produce normal amounts of the pigment melanin. Melanin is responsible for giving colour to the skin, hair, and eyes. The disorder is caused by inheriting two copies of a recessive gene that codes for a defective or non-functional form of the enzyme tyrosinase, which is needed for melanin synthesis.

Since albinism follows an autosomal recessive inheritance pattern, an individual must receive the defective allele from both parents (homozygous recessive, aa) to express the condition. A person who carries only one copy of the recessive allele (heterozygous, Aa) is a carrier but does not show symptoms because the dominant allele produces enough functional enzyme.

The other options are incorrect. Sebum is an oily substance produced by sebaceous glands in the skin that lubricates the skin and hair; it plays no role in pigmentation. Over-production of melanin would result in hyperpigmentation (darker skin), not albinism. The root cause is genetic, not a simple over- or under-production of a glandular secretion.

Exam tip: Albinism is a classic example of a condition caused by homozygous recessive alleles. Remember that the underlying mechanism involves a faulty enzyme (tyrosinase) leading to absence or severe reduction of melanin.