Chromosomal rearrangements caused by the aberrant transposition of double Ds elements are formed by Ds and adjacent non-Ds sequences.

The Ds-induced unstable sh-m6258 allele is caused by the insertion of at least 45 kb of non-sh DNA. Genomic clones spanning the two junctions of sh sequences with insert sequences were isolated and analysed. The long insert in the sh-m6258 allele is bordered by Ds sequences on either side.