The Fragile X syndrome - K. E Davies

Controversy and difficulties of definition and diagnosis have surrounded the mental retardation syndrome associated with a gap in the X chromosome ever since it was first described some 25 years ago. Individuals who are affected show varying degrees of retardation, an elongated face and macro-orchidism. It is generally agreed that the condition is second only to Down Syndrome as a specific cause of mental retardation.;The syndrome is more common in boys than in girls, but can be inherited from either parent, so each case diagnosed necessarily involves the investigation of an extensive number of relatives. To date the precise nature of the defect is unknown, but it has been mapped with the aid of DNA probes. These probes can be useful for tracing inheritance within a family, for detecting carriers, and for assisting in the laboratory in attempts to isolate and characterize the defect, which should lead to improvements in pre-natal diagnostic techniques and in the clinical management of patients.;This volume contains a series of essays designed to introduce and review clinical and biological knowledge of the mental retardation syndrome for a non-specialist audience. Current research and development is examined, and experts in the field attempt to point the way for future work.