Fate of donor insertion sequence IS1 during transposition.

Abstract
The number of insertion sequence IS1 segments in Escherichia coli K-12 and 20 mutants in which an IS1 was inserted at a new site was measured by Southern blot hybridization analysis. The parent strain appeared to contain seven IS1 segments. Each of the mutants contained these 7 IS1 and 1 additional IS1 corresponding to the new IS1 insertion. A copy of a donor IS1 is inserted at the new site. A model for transposition is presented that postulates that a reactive intermediate is formed by a tandem duplication of a transposable sequence.