The scheme of P-element transposition. The illustrations show a model of P-element mediated transposition. First, the transposase binds to sequences within both P-element termini and initiates a DSB at each end. The excised P-element could be translocated into a new target site to disrupt another gene (left). Gap repair can then generate duplicated target sites with the P-element sequences at each end. The 3′ extensions left at the donor site can be used for repair either from homologous sequences located in the other copy as a fully repaired gene which contains two adjacent P-element target site (top right), or by non-homologous end-joining for imprecise repair, which could generate products that contain varying lengths of P-element-derived sequences as the imprecisely repaired condition (bottom right).