The study of genetic variation in Nigeria. II. The genetics of polydactyly.

The analysis of polydactyly in the Nigerian population has revealed a frequency of 22.78 per thousand, with slight variations from one region of the country to another. All polydactyly was post-axial and most was of type B. Although we expected this frequency to be the same in both males and females, we observed that females have a significantly lower frequency (17.92 per thousand) than the males (27.08 per thousand). This condition appears to be inherited as an autosomal dominant gene with a penetrance of 64.9%, and highly variable expressivity. There does not seem to be any phenotypic difference between individuals who are homozygous and those who are heterozygous for the gene.