Barbara McClintock (1902–1992) investigated inherited variation in maize, combining chromosome observations with the transmission of visible traits. Her work identified mobile controlling elements, now understood as transposable elements, showing that genetic regulation need not be represented by permanently fixed gene positions.[ref]
The origin and behavior of mutable loci in maize by Barbara McClintock. 1950, pp. 344–355
Coloured and uncoloured sectors in maize tissues provided an observable record of changes occurring during biological development. Connecting those patterns to genetic and cytological evidence made movement and regulation experimentally testable. She received the 1983 Nobel Prize in Physiology or Medicine for the discovery of mobile genetic elements.[ref]
https://www.nobelprize.org/prizes/medicine/1983/summary/. Official award record
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Barbara McClintock (1902–1992) was an American scientist and geneticist who is best known for her groundbreaking work in the field of genetics, particularly in maize (corn). She was awarded the Nobel Prize in Physiology or Medicine in 1983 for her discovery of "jumping genes," or transposable elements. McClintock's research demonstrated that genes could change positions on chromosomes and that this could affect the expression of traits in organisms.