A transposed fragment containing w sequence derived from the w^67c23 allele is inserted within the first intron of osp (at nucleotide position 248479 of accession AE003410). The fragment encompasses the first intron of w and extends downstream for approximately 14kb. The fragment is bounded by FB elements and also contains NOF sequences within it. A direct repeat of 9bp is present on both sides of the insertion. A chimeric mRNA is produced, consisting of exon 1 of osp (the exon upstream of the insertion point) fused to the w sequences (starting at w exon 2). This is predicted to produce a polypeptide containing 658 out of the 687 amino acid residues of the w product with an N-terminal extension of 71 amino acids encoded by the upstream osp exon.