American geneticist Barbara McClintock, who challenged the prevailing theory that genes were stable components of chromosomes with her discovery of "jumping genes," was born on this day in 1902. McClintock studied inheritance in corn, examining the patterns of color appearing in the kernels and leaves.
In 1931, McClintock and graduate student Harriet Creighton proved that the physical mixing of chromosomes could lead to the exchange of genetic material. By 1944, McClintock had observed that certain genes hopped from cell to cell as a kernel developed. Four years later, she discovered that controlled breakage of chromosomes was what was allowing the genes to move. When McClintock published the surprising finding in 1950, the scientific community was skeptical, but in 1983 she was awarded the Nobel Prize in physiology or medicine. Her work was later used to explain inheritance patterns that did not follow Mendelian rules based on dominant and recessive traits. McClintock died in 1992.