Internal Rearrangements of IS2 in Escherichia coli

Mutations caused by the insertion of movable genetic elements are often accompanied by regional destabilization of the chromosome. This instability is a direct consequence of processes (such as inversions, deletions, or excisions) promoted by these elements that constitute the bases of the seemingly diverse phenomena discussed at this Symposium. Although most of these phenomena stem from alterations of the adjoining regions of the chromosome, these elements also promote internal rearrangements that contribute to their novel, and often bewildering, properties. In this article we describe some internal sequence alterations of IS2 that were detected as revertants of the gal3 mutation of Escherichia coli. We explain the unusual behavior of these revertants in terms of special features of their DNA sequences.