Fragile X syndrome is a mental condition caused by the mutation in a single gene called the fragile X mental retardation 1 (FMR1) gene, which is found on the X chromosome. Fragile X syndrome is the most common inherited condition causing mental retardation. Fragile X syndrome can cause learning disabilities, severe mental incapacitation and even autism. Behavioral features exhibited include problems with speech, poor eye contact and attention deficit disorders. At this time, there is no cure for fragile X syndrome. Evidence suggests that fragile X syndrome might involve abnormal development of neuronal structure in the brain. The reason for this study is to determine whether there are density and length differences in the dendritic spines of normal wild-type mice and affected homozygous mice.