The fragile-X syndrome.

The variability in behavioral manifestations of the fragile-X syndrome and the lack of a well-defined psychological profile require the attention of behavioral geneticists and other behavioral scientists. The association with autism suggests that the fra(X) may be responsible for a genetic subtype of autism. While the fragile-X syndrome is considered an X-linked disorder, several aspects of observed transmission patterns do not follow those of classical X-linked inheritance. In particular, the finding of genetic transmission via intellectually normal males is surprising and has important implications for genetic counseling, as well as for genetic models of the fragile-X syndrome. Reports on folic acid treatment are encouraging, but not conclusive. The mechanisms involved in the association between the fra(X) chromosome and its particular phenotype are still unknown. Current investigations applying advanced techniques in molecular biology are likely to provide insight into this unique genetic disorder.