transposon

A movable DNA element that can be inserted at new sites into plasmids or chromosomes independently of the host cell recombination system. Prokaryotic transposons can carry genes that confer new phenotypic properties, such as resistance to antibiotics on the host.
Source:
PAC, 1992, 64, 143 (Glossary for chemists of terms used in biotechnology (IUPAC Recommendations 1992)) on page 167