An expanded GAA triplet-repeat from the first intron of the human Hsap\FXN gene, with a GAA repeat length of about 200 units and obtained by PCR from the genomic DNA of a patient with Friedreich ataxia, has been inserted into the intron of the orthologous D. melanogaster fh gene. The Hsap\FXN sequence includes sequence from the human first intron flanking each side of the GAA expansion (157bp upstream and 125bp downstream sequence).