[DNA diagnosis of the fragile X chromosome syndrome--FRAXA using PCR].

BACKGROUND: Fragile X syndrome is gonosomal recessive mental retardation with the frequency 1:1000 in male population. Fragile X syndrome is caused by amplification of CGG repeat in 1. exon of FMT-1 gene. The aim of this study was to set up and validate a rapid and efficient PCR diagnosis to select FRAXA negative patients in population of mental retarded patients. METHODS AND RESULTS: In the set up phase of the method, 196 patients were diagnosed. We were using modified radioactive PCR of CGG. Obtained PCR fragments were separated on 6% denaturing PAGE. Results were correlated with Southern blot analysis using pE5.1 probe. STR-PCR was verified on a large set of patients and shows validity and efficiency of results in the case of pre- and full mutations in male hemizygous patients too. For estimation of carriers with pre- and full mutation by females modified diagnostic approach was developed. There was no difference found between results from PCR and Southern blot analysis. CONCLUSIONS: The PCR method is convenient not only for selection of FRAXA negative patients, but for diagnosis of full mutation and premutation of affected probands.