= DNA transposon
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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.<A unified classification system for eukaryotic transposable elements by Thomas Wicker and others>[Opening classification framework and classII subdivisions]{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.<P element in FlyBase>[Transformation-vector and transposase-source sections]{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.
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