 McClintock was widely credited for discovering transposition after other researchers finally discovered the process in bacteria , yeast , and bacteriophages in the late 1960s and early 1970s . During this period , molecular biology had developed significant new technology , and scientists were able to show the molecular basis for transposition . In the 1970s , Ac and Ds were cloned by other scientists and were shown to be Class II transposons . Ac is a complete <unk> that can produce a functional transposase , which is required for the element to move within the genome . Ds has a mutation in its transposase gene , which means that it cannot move without another source of transposase . Thus , as McClintock observed , Ds cannot move in the absence of Ac . <unk> has also been characterized as a <unk> . Subsequent research has shown that transposons typically do not move unless the cell is placed under stress , such as by irradiation or the breakage @-@ fusion @-@ bridge cycle , and thus their activation during stress can serve as a source of genetic variation for evolution . McClintock understood the role of transposons in evolution and genome change well before other researchers grasped the concept . Nowadays , Ac / Ds is used as a tool in plant biology to generate mutant plants used for the characterization of gene function . 
