The syndrome is caused by the genetic inability to normally produce the protein. There is no cure. Fragile X refers to the broken appearance of the X chromosome when cells are cultured under specific conditions. The gene was found in 1969, but the link to mental retardation was not known. Despite being sequenced and named the Fragile X Mental Retardation Gene in 1991, its mechanisms remain a mystery.
Mothers pass the gene to their sons.
Impairment ranges from slight to severe retardation. The fragile X gene contains the genetic code for the fragile X protein. The code is transferred from the gene into messenger RNA and transported to a distant synapse where it acts as a template for producing the protein, said Greenough, who also is a professor of psychiatry and of cell and structural biology. This finding points to a mechanism of action of the protein that may account for the mental retardation. Previous research involving autopsies of humans had shown immature synapse formation, but it failed to show impairment of the synapse pruning process, in which excess synapses are deleted.