A gene at 15q21.1 in humans that encodes a protein which functions as a cation exchanger in melanosomes. The gene exists in two allelic forms varying at one codon. The ancestral form (A) is present in most African populations, while the derived form (a) is present in most Europeans. AA individuals are dark skinned, aa are light skinned, and Aa are intermediate. This polymorphism accounts for most of the skin pigmentation differences between human races. See Chronology, 2005, Lamason et al.; melanin, melanocytes.
Subjects: Genetics and Genomics.