4Tn2

4Tn2 is a fictional genetic element used in teaching resources to illustrate the behavior of mobile DNA in bacteria. The designation combines a conventional transposon label (Tn) with a model number that signals a fourth-generation example and a second variant. It is not described as existing in any real organism outside classroom simulations and textbooks.

In the educational model, 4Tn2 consists of a transposase gene, a short inverted-repeat boundary, and a cargo region that can carry selectable markers or metabolic traits. The element is depicted as roughly 2–3 kilobases long, with the transposase belonging to a family of enzymes that mediate cut-and-paste transposition. Cargo and repeats are arranged to illustrate mobility and containment.

Mechanism in the module shows excision from a donor site and insertion into a new target site, following a simplified, non-replicative pathway. The scenario highlights typical transposon behavior: excision, target selection, and stable integration. By including a cargo gene, the model also demonstrates potential effects on host fitness and genomic context.

This fictional element originated in the 2010s within open-education materials designed to illustrate genome dynamics. It appears in classroom exercises, simulations, and introductory texts as a clear example of how mobile elements carry cargo and influence microbial genomes. It is explicitly labeled as a didactic construct and not a real sequence.

See also and references. Related topics include transposons, mobile genetic elements, and horizontal gene transfer. Because 4Tn2 is fictional, there are no primary research references; readers are directed to general biology texts for real transposon examples such as Tn3, Tn10, and IS elements.