[Molecular biologic screening test (PCR) for fragile X syndrome].

Fragile X syndrome is the most common inherited from of familial mental retardation. It is caused by an expanded CGG repeat in the first exon of the fragile X mental retardation gene. A polymerase chain reaction based technique was used for the identification of full mutations among men. According to our conditions full mutations failed to amplify. An internal control was used at a CG rich region 147 bp upstream of the polymorphic region. The bands were visualised on silver stained polyacrylamide gels. From the 57 individuals studied molecular analysis was performed on 38 males and 16 females. From the 26 males with suspected fragile X syndrome 9 males resulted in no amplification of the 500 kb product, all having a positive cytogenetic result for fragile X syndrome. One cytogeneticly positive male had normal results by molecular studies suggesting a different mutation. All control males had normal results. The results on the 16 females studied were inconclusive. We suggest that our method is highly sensitive and specific for screening males for fragile X syndrome.