Rapid preparation of diagnostic probes for the fragile X syndrome by direct PCR amplification of human chromosomal DNA

Summary The fragile X syndrome is a common familial form of mental retardation and is associated with a rare fragile site at Xq27.3 (FRAXA). This disorder has recently been reported to correlate with length variations of restriction genomic DNA fragments which may due to the amplification of (CCG)_n trinucleotide repeats located at the FRAXA locus. We described here a rapid preparation method of diagnostic DNA probes for the fragile X syndrome by direct enzymatic amplification of human chromosomal DNA. ThePstI-assay, which is Southern blot analysis of DNA samples probed by PCR products, was shown to be sensitive method for diagnostic purposes to detect the size variations specific in the fragile X syndrome.