 DNA transposon

A DNA transposon is a transposable element whose mobilization proceeds through a DNA intermediate rather than through an RNA intermediate. This distinguishes it from a retrotransposon. It does not by itself specify whether a particular event removes the original copy, creates an additional copy or requires machinery supplied by another element.^[ref]

An original copy-location model separates the questions. Start with one copy at a donor site and none at a recipient site. A cut-and-paste model ends with zero at the donor and one at the recipient; a replicative model ends with one at each. The totals are one and two, respectively. Both are DNA-level bookkeeping models. Establishing a real mechanism requires evidence about the molecular intermediate and the fate of the donor, rather than only observing a changed total gene copy number.

The P element supplies a concrete experimental system. A P-element vector can retain mobile recognition sequences around inserted cargo while P-element transposase is supplied separately. The carrier's recognition sequences and the enzyme's coding sequence are therefore distinct functional components.^[ref] Not every DNA transposon must encode its own active enzyme, and the detailed P-element arrangement should not be imposed on every other family.