Figure 1. DNA transposition. The transposon ends are red, the target insertion site is yellow and the target DNA is green.

Figure 2. Comparison of transposition pathways. Grey segments represent transposable DNA elements. Small arrows indicate phosphodiester bond breakage, as discussed in the text (Basic reactions). Solid and dotted lines represent donor and target DNA, respectively.

Figure 3. Basic reactions. (a) During cleavage at each end, an activated water molecule serves as a nucleophile to attack a phosphodiester bond. The opposite strand may or may not be released, depending on the transposon. In some systems, cleavage occurs via a hairpin intermediate as depicted. When the hairpin is resolved by hydrolysis, the transposon is left with a blunt end. (b) Strand transfer occurs via staggered insertions, one in each target strand. The result will be single-stranded gaps adjacent to each end that, when repaired, result in target site duplications.