Recombinant DNA approach to X-linked mental retardation.

Currently, approximately 115 X-linked diseases have been documented. Many of these defects are neurological in nature and about 25% result in a broad spectrum of mental impairments which can be distinguished by biochemical or clinical means. It is not known how many of the retarded population carry an X-linked defect due to lack of a distinct marker. By constructing a molecular linkage map of the X chromosome using DNA polymorphisms, it will be possible to identify these individuals, classify their disorder by the chromosomal region in which their polymorphism is detected, offer genetic counseling and prenatal diagnosis to their family members and try to determine which gene the polymorphism is linked to in order to identify the defect and devise therapy.