Barbara McClintock discovered transposable elements in maize and won the 1983 Nobel Prize in Physiology or Medicine.
While studying corn chromosomes in the 1940s and 1950s, McClintock observed that certain DNA elements could move within the genome and alter the activity of nearby genes. She called them controlling elements; they are now commonly called transposable elements or transposons.
Her findings were initially difficult for many researchers to accept because genes were often viewed as fixed points on chromosomes. Later molecular studies showed that mobile DNA is widespread in bacteria, plants, animals, and humans.
Transposons can influence gene regulation, create mutations, and reshape genomes. They are different from ordinary point mutations because their defining feature is movement or copying of a DNA element to another genomic location.