Barbara McClintock, who has died within a few months of the publication of a Festschrift celebrating her ninetieth birthday, was probably the most famous of living geneticists. Her almost legendary status is based on her discovery of transposable genetic elements ('jumping genes'), but perhaps even more on her solitary style of work and total independence of spirit.
Her common portrayal as an outsider, denied recognition by the scientific establishment, is somewhat misleading. In the earlier part of her career, based largely on Cornell University, she made a unique and important contribution to the work of the pioneering group, led by RA Emerson and including such eminent scientists as George Beadle and Marcus Rhoades, that developed maize (corn in the American sense) as an exemplary plant for classical cytogenetics. Her outstanding skill and perceptiveness as a microscopist enabled her to distinguish all the maize chromosomes and correlate each of them with a linked group of genes. A little later, a combination of microscopy and clear genetic reasoning led her, in collaboration with Harriet Creighton, to a formal proof that recombination of linked genes was due to physical exchanges between chromosome segments; the resulting paper was remarkable both as a scientific landmark and as the only example, so far as I know, of McClintock's publishing other than as solo author. In 1944 she was elected membership of the National Academy of Sciences of the US - only the third woman ever to be accorded that honour.
In 1941 she accepted a position at the Carnegie Institute of Washington at Cold Spring Harbor, Long Island, and remained there for the rest of her life. By the mid- 1940s she had made the first observations of gene instability in maize - an instability that she was able to attribute to movable genetic elements.
Her first full public exposition of her observations and conclusions was at the Cold Spring Harbor Symposium of 1951. The response was a sad disappointment to her. There was, by all accounts, an almost total lack of comprehension on the part of the audience. The idea of movable genes was difficult to assimilate, especially when there was no mechanistic hypothesis to make it more digestible. It was not that McClintock lacked evidence. Indeed, she provided far more than the audience could take in, with every paragraph loaded with results condensed from years of devoted work at the bench and in the cornfield. The most favourable reactions showed uncomprehending respect. Alfred Sturtevant, one of the great originators of the chromosome theory, was quoted as saying that he didn't understood a word of it, but since Barbara had said it he guessed it must be right.
McClintock had another try - with yet more apparently bizarre detail - at the 1956 Cold Spring Harbor Symposium, but it took longer than that for the rest of the genetical world to catch up with her. Her eventual reassimilation into the mainstream was due partly to the repetition and extension of aspects of her work by other maize geneticists, but more decisively to the authentication of movable genetic elements as identifiable DNA sequences, first in bacteria and fruit-flies in the 1970s and then, in the early 1980s, in maize and other plants. What McClintock said had always been true; it was now believable as well. She received the Nobel Prize in 1983.
There is now a considerable army of molecular biologists reinvestigating Barbara McClintock's conclusions at the molecular level. Everything makes sense, but whether it is the kind of sense she would have hoped for is another question. Her 'feeling for the organism' (to quote the title of Evelyn Fox- Keller's account of her life and work) led her to believe that her elements were an integral part of the biology of the plant. Though I have never seen her quoted on the subject, I doubt whether she found the idea that they were 'selfish DNA' or molecular parasites much to her taste, compelling as this seems to some of us.
Barbara McClintock was a unique person as well as an outstanding scientist. This small, almost elfin lady, so dynamic and eager to understand and share her understanding with others, made a great impression on all who met her. She always had time for people, especially, perhaps, for the young. As a totally unknown graduate student, I had the lucky opportunity to visit her in 1948 and 1949, and on each occasion she treated me to a long and unforgettable exposition of the current state of her work. She concluded, I remember, by advising me to take the opportunity of hearing the new wave of bebop jazz musicians then performing in New York City. She herself had played the banjo in a jazz group in former years.
Yet, beneath the vivacity, she was a rather reserved and private person. Some who knew here well have described her as a mystic, but she never committed her inner philosophy to print. Her reported observations were all perfectly objective, open to all the world to repeat. The scenario that she built from them in her own mind was perhaps never fully revealed to us. What is certain is that she knew how to look, and had the confidence to believe what she saw.
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