Posted in Science Stories

Barbara McClintock: Transposable Elements in Maize

Unexpected scientific discoveries are usually made by people who are so fascinated by the focus of their research that they probe deeply enough to find and illuminate the hitherto unknown lurking within it. They don’t begin their work hoping for acclaim or awards, but immerse themselves in it for the sheer pleasure of knowledge and discovery. (In this sense, it’s very much like free and self-directed play in small children exploring the world around them, and is powered by the same intrinsic motivation to find out why and how things work.)


Barbara McClintock, the discoverer of transposable elements, was a profound example of this general rule. From a young age she loved science and overrode her mother’s fears about her marriageability to enroll at Cornell in 1925, where she was introduced to the nascent field of genetics, just twenty-one years after the rediscovery of Mendel’s studies on the heritability of traits in peas. While her initial discovery of transposons was well-received, most scientists in the field were skeptical of her hypothesis that transposable elements could act as regulatory elements and thus control the expression of genes. In fact, until bacterial geneticists discovered the operon in the 1960s, most scientists were doubtful that some elements within the chromosome – especially movable elements! – exercised control over other elements. McClintock, however, dove deeper into her obsession with the idea of genetic control, attempting to weave the hard data from her experiments into a better theory of inheritance. Given the tools at her disposal, it is amazing how much she was able to discover through the sheer force of her curiosity and determination.

While not all of her hypotheses were correct (transposable elements are much more of an agent in evolutionary change in organisms than in embryonic development paths, since their regulation of genes is more akin to random mutation than purposeful direction), her meticulous research and intuitive logical understanding of the results gained her immense respect, admission to the National Academy of Sciences, and, near the end of her life, a Nobel Prize – the first solo Nobel Prize of that category to ever be awarded to a woman. Through all the accolades, however, her drive remained the same; in the words of her biographer Nathan Comfort, “McClintock’s guiding principle was to embrace and investigate the complexity of nature.” In other words, she abandoned social posturing and competition for the primal joy of play: exploration at the edge of the known world.


The Barbara McClintock Papers, U.S. National Library of Medicine,

Comfort, N.C. (1999) “‘The Real Point is Control’: The Reception of Barbara McClintock’s Controlling Elements,” Journal of the History of Biology 32: 133-162, PDF of Article

Pray, L. & Zhaurova, K. (2008) “Barbara McClintock and the discovery of jumping genes (transposons).” Nature Education 1(1):169, Link to Article

Kolata, Gina. (1992) “Dr. Barbara McClintock, 90, Gene Research Pioneer, Dies.” The New York Times, Link to Article


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