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Transposon - Jumping Genes Transposable Genetic Elements

Transposon - Jumping Genes Transposable Genetic Elements - Transposons:
 They are the so called jumping genes for which Barbara McClintock won the 1983 Nobel Prize in Physiology or Medicine. Earlier in 1951, her work on Indian corn plants revealed that genes may not be always fixed elements and found in the same position on the same chromosome. She could describe that genes apparently moved from one chromosome to another. She watched over the changes in colour in her plants and the pigment genes responsible for colour change appeared to be switched on or off in particular generations.

More remarkable was that these switches occurred in later generations at different places along the same chromosome. In modern molecular genetics, these controlling elements are a two element system: an activator gene and the other a dissociation gene. The activator gene can direct a dissociation gene to jump along the arm of the ninth chromosome in maize plants where colour is regulated.

Jumping gene is identical to 'the transposon found in bacteria. Transposons, first identified and named in 1974 by British Microbiologists, R.W. Hedges and A.E. Jacobs, are larger than insertion sequences and carry information for protein synthesis. They contain genes for antibiotic resistance. They may move from plasmid to plasmid, from plasmid to chromosome or from chromosome to plasmid. The movement of transposons is nonreciprocal i.e. an element moves away from its location and nothing takes its place. This contrasts with insertion sequences where copies move.
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