Bidirectional deletions associated with IS4.

A new type of chromosomal rearrangements associated with a transposable element has been described for IS4. These rearrangements are deletions, in which the transposable element IS4 and DNA adjacent to it on either side is lost. These deletions are at least ten times more frequent in the presence of IS4, than when the element is absent from that region. The formation of bidirectional deletions is more than 1,000 times more frequent than precise excision of IS4.