X‐linked mental retardation: Transmission of the trait by an apparently unaffected male

Abstract
A pedigree is presented in which an apparently unaffected man transmitted the gene for X‐linked mental retardation to at least four of his 12 daughters. None of his 12 sons was mentally retarded. These findings may be explained by a somatic mutation and germinal mosaicism in the father or by a half chromatid mutation in maternal gametes.