How were transposons first discovered in bacteria?
The first transposons to be discovered were found in maize plants. Barbara McClintock described them during the 1950’s from experiments carried out in the 1940’s, before the structure of DNA had been elucidated. They were shown to be responsible for a degree of genetic instability in plants. During the 1960’s it became apparent that bacterial genetic systems, like their eukaryotic counterparts, were also subject to genetic instability. The emergence and spread of antibiotic resistance particularly facilitated the study of this instability. By exposing mixed populations of bacteria to antibiotics in culture, those cells that carry a gene or genes conferring resistance to the antibiotic can easily be selected. They will grow, whilst sensitive bacteria will be inhibited or killed by the antibiotic, which acts as a selective agent. The first bacterial transposon to be described was found on a plasmid, RP4, which encodes resistance to ampicillin, kanamycin and tetracycline resistance. Hedge
