Friday, December 17, 2010

Life Lines 89


Barbara McClintock won an unshared Nobel prize in Medicine in 1983. She was already advanced in age when she won that award and many others, including the MacArthur Award, a no-strings attached generous award given to geniuses. McClintock grew up in Brooklyn and went to Cornell for her undergraduate education. She liked botany and soon proved herself to be uncommonly gifted in cytology, the study of cell chromosomes and other structures in the cell. She worked exclusively in corn genetics and cytology the rest of her life. It was not easy for a woman to get a faculty job in those days and she held low paying jobs in Missouri and later at Cold Spring Harbor. This wasn’t too important for McClintock, because she never married and lived simply, spending most of her life in the fields caring for her corn and in her laboratory looking at the results of her genetic crosses and confirming her interpretations by careful study of the chromosomes under a microscope.

McClintock worked with a genetically difficult organism. When you munch on a corn kernel, it contains three tissues – a maternal tissue that has two sets of chromosomes (two sets is normal), a nutritive material that has three sets of chromosomes, and its own tissue, including the embryonic leaves, roots, and stems, that have two sets of chromosomes. Corn also takes some time to grow and at best McClintock could get two growing seasons a year. She also worked on problems that intrigued her. She was the first to show how chromosomes produce genetic recombination. She mapped all of the chromosomes in corn. She discovered a curious phenomenon that she called the breakage-fusion-bridge cycle that became the basis of interpreting radiation sickness from those who are heavily exposed to radiation, like victims of Hiroshima and Nagasaki. Her Nobel was given to her for something even more unusual. She claimed in the early 1950s that she had found genes that detached from chromosomes and inserted themselves elsewhere. She called them “transposable elements.” They were later found in bacteria and other plants and animals. They are now a major tool for genetic engineering and bring human genes into bacteria, mice, or sheep.

I heard McClintock give papers on her work when I was a graduate student but I didn’t understand the significance of her work. She didn’t have much opportunity to teach so her presentations tended to be very technical and difficult to follow for those not in corn genetics. When my wife and I honeymooned on Cold Spring Harbor, we got to know her well and she always had a cheery greeting when I passed her while she worked in the field. About 1970 she called me and asked if I wanted their reprint collection for my history of genetics studies. I drove out with an undergraduate student. “Have a lollipop,” she said, when we got there and then my student and I had a wonderful discussion with her on her idea about genetics.

McClintock had misgivings about a biography written about her. “It makes me feel like a cult figure,” she lamented and with reluctance she autographed my copy. She treasured her privacy and was one of those rare individuals who thrived on solitude and the pleasure of a life in science.

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