Tc and mariner elements.
Transposase-mediated cleavage at the terminal 3' phosphodiester bond and at a position of 2 nucleotides within the 5' ends is indicated by curved arrows. Excision of the element (grey box) leaves two 2 nucleotide 3' extensions in the vector backbone (open flanking box). Insertion is thought to occur by simple nucleophilic attack by the free 3'OH groups of a specific TA target dinucleotide as shown by the long curved arrows. Repair of the donor backbone will leave a 2 bp insertion (footprint) compared to the original target sequence