Excision of Tn<i>6283</i> from the <i>E</i>. <i>coli</i> chromosome.

<p>(A) Design for PCR detection of recombination products. The diagrams show the hypothetical scenario in which Tn<i>6283</i> excises itself as a circular molecule and forms a heteroduplex joint, while the Tn<i>6283</i> donor site also forms a heteroduplex joint. The PCR-amplified heteroduplex joints should contain two types of sequences in the spacer between terminal repeat sequences. (B) PCR detection of joint formation on the recombination products. Lane 1: long PCR designed to detect the occupied Tn<i>6283</i> donor site (primer set 2599572R-2599370F). Lane 2: detection of unoccupied Tn<i>6283</i> donor sites (primer set 2599572R-2599370F). Lane 3: detection of circularized Tn<i>6283</i> (primer set 3F-3R). (C) Sequences of PCR-amplified joints on the circularized Tn<i>6283</i>. The observed frequency is indicated next to each sequence. (D) Sequences of PCR-amplified joints on the unoccupied Tn<i>6283</i> donor sites. In the upper panel, two types of expected joint sequences are shown. The lower panel shows the unexpectedly observed sequence, designated Scar.