X-Linked mental retardation with fragile X. a pedigree showing transmission by apparently unaffected males and partial expression in female carriers

Abstract
A large family is reported in which mental retardation associated with the fragile site at Xq28 was found. Three normal males seemed to have transmitted the trait through their daughters to affected grandchildren. A total of 19 family members were investigated cytogenetically. Mentally retarded males showed macroorchidism and the fragile X. Three mentally retarded females were found, with the fragile X in a high percentage of cells; in contrast, the obligate carriers showed no or only few cells with the fragile X.