Barbara McClintock discovered the first known transposable elements in maize before they were called jumping genes.
While studying corn chromosomes, McClintock found genetic elements that could move to different locations in the genome. She called them controlling elements and showed that their movement could switch nearby genes on or off, producing visible changes in kernel color.
The idea was far ahead of the molecular biology of the 1940s and was initially received skeptically. Later research established that transposable elements are widespread in organisms and make up substantial portions of many genomes.
McClintock received the 1983 Nobel Prize in Physiology or Medicine, becoming the only recipient of that prize that year. Her work helped reveal that genomes are dynamic rather than fixed strings of genes.