Plastic model of the Tn5 transposase

Some DNA fragments can change their own location in the genome. Such fragments are called transposable elements (TEs) or transposons. Transposable elements are found in almost every organism — from bacteria to higher eukaryotes, including humans — and they play a crucial role in evolution because they are a powerful source of genetic variability. Transpositions and rearrangements of genetic material are normal and often beneficial for the species, but in many cases they may cause harm or death to an organism.

Most TEs carry one or more genes encoding the proteins necessary for transposition. Transposases are among such proteins. The transposase enzyme shown here is encoded by the Tn5 transposon, which is found in bacteria.

Tn5 is among the first described transposons [1]. It was discovered in Escherichia coli during studies of bacterial resistance to the antibiotic kanamycin.