Jumping genes or movable genetic elements were discovered by Barbara Me Clintock (1902-92) in maize. These controlling elements could move from one location to another on the chromosome. Barbara Me Clintock got the Nobel Prize for these genetic elements (Ds= Dissociation gene, Ac = Association gene) which can jump to any chromosome from their original location on chromosome. The term transposon was introduced by RW Hedges and AE Jacob (1974) to these genetic element (jumping gene). Hugo de Vries introduced the term mutation, in connection with the studies on Oenothera lamarckiana (evening primrose). His theory is known as mutation theory. TH Morgan proposed the gene theory (linkage of genes) and crossing over. Gregor Jonann Mendel (1822-1884) is known as the father of genetics. The first scientific study leading to formulation of laws of inheritance was carried out by Mendel.