DNA transposition is the relocation or insertional copying of a defined DNA segment through the action of transposition machinery. The DNA transposon is the mobile sequence; DNA transposition is the process. In a DNA-mediated system, transposase recognizes the relevant ends and coordinates their chemical processing and transfer into target DNA. Individual systems differ in whether a donor copy is removed or retained.[ref]
A unified classification system for eukaryotic transposable elements by Thomas Wicker and others. DNA-intermediate classification and mechanistically distinct classII groups
The Tn5 system reveals how two ends can be coordinated. A 2000 structure of Tn5 transposase bound to transposon-end DNA showed two protein subunits organizing the ends into catalytic positions. Each end contacted both subunits, and the structural model explained how end recognition and cleavage could involve different subunits.[ref]
For a bookkeeping example, label a mobile segment
X. An excision assay can establish that the donor junction changed from A-X-B to a repaired arrangement lacking X. That observation alone does not locate X elsewhere. A new recipient junction containing X establishes an additional event. Measuring DNA transposition therefore requires distinguishing end recognition, cleavage, target insertion and subsequent DNA repair, rather than treating any one signal as proof of every step. New to topics? Read the docs here!