The Genetics of Red Hair

Population and family studies support, with few exceptions, the hypothesis that there is a gene which leads to freckles and brown hair in the heterozygous individual, and freckles and red hair in the homozygote. The frequency of this gene is five times greater in those of Northern European ancestry than it is in those of Mediterranean ancestry. The frequency of pigmented birthmarks in the different phenotypic classes is consistent with the hypothesis that many of these birthmarks result from somatic mutation occurring in this gene.