Direct detection of loci with pathologic trinucleotide repeats in diseases with anticipation

: We describe a simple method for the identification of pathologically expanded (CCG)n and (CTG)n three nucleotides repeat arrays in the human genome and for the recovery of flanking sequences. We were able to detect the presence of novel high-molecular-weight alleles in at least two of three subjects known to have expanded (CCG)n tracts at the FRAXA locus. The above method may be used for testing of small families or even single affected individuals with disease thought to display clinical evidence of anticipation. The (CCG)n > 200 and (CTG)n > 250 probes may also be useful for individual "DNA fingerprint" identifications.