Generation of a widespread Drosophila inversion by a transposable element

Although polymorphic inversions in Drosophila are very common, the origin o f these chromosomal rearrangements is unclear. The breakpoints of the cosmo politan inversion 2j of D. buzzatii were cloned and sequenced. Both breakpo ints contain large insertions corresponding to a transposable element. It a ppears that the two pairs of target site duplications generated upon insert ion were exchanged during the inversion event, and that the inversion arose by ectopic recombination between two copies of the transposon that were in opposite orientations. This is apparently the mechanism by which transposa ble elements generate natural inversions in Drosophila.