[DNA duplications detect the hidden transposition of the Tn5 element in the Escherichia coli K12 genome]

The frequency of Tn5 transposition localized in an arm of a tandem duplication was estimated as 1.3 X 10(-2) per cell per generation, two orders of magnitude higher than usual one. Approximately thirty per cent of all transpositions usually registered occur from the spontaneous duplications. The effect revealing latent transpositions is in good accordance with a conservative transposition model permitting some interesting predictions: 1. Composite transposons can be a reason for the double stranded cuts in DNA. 2. The transposition frequency in cis for composite elements seems to be many times higher than in trans. 3. Partially transpositions in cis can be recA dependent. 4. The estimation of Tn5 transposition in cis presented in the paper is a minimal one.