Barbara McClintock, shown here at Cold Spring Harbor
Laboratory on Long Island, New York, spent more than half a
century analyzing color differences and other variations in
corn kernels (each of which is actually an embryonic corn
plant). On the basis of mapping studies, analogous to those
carried out with Drosophila in Morgan's laboratory, she
deduced that the changes she observed were not the result of
ordinary mutations. Instead, she postulated, the changes came
about as a result of the movement of genes, or "controlling
elements," that jumped from one place to another on a
chromosome - or even from one chromosome to another.|
McClintock's findings, first published in 1951, were largely ignored. Like Mendel before her, she was a lonely traveler with an odd tale that did not fit into the scheme of things as then understood. James Watson, who has also worked at Cold Spring Harbor (first as a nineteen-year-old graduate student, then as its director from 1968 to 1993, and now as its president), once described McClintock as "fiercely independent, beholden to no one." Despite the lack of recognition, she stubbornly pursued her research, sometimes working without pay. "It was fun," she said, "I could hardly wait to get up in the morning."
McClintock was more than vindicated by a rush of discoveries, some 30 years later, of a host of movable genetic elements such as those she had first postulated. "Jumping genes," or transposons, as they came to be known, move from place to place on the chromosome and influence the expression of other genes. When McClintock was 81 years old, she received the Nobel Prize.
Her life did not change much, however. She continued her work at Cold Spring Harbor until shortly before her death in 1992 at the age of 90. "There are really three main figures in the history of genetics," Watson noted at a tribute to her the year before. "The three M's: Mendel, Morgan, and McClintock. Gregor Mendel and Thomas Hunt Morgan showed us how regular the genome is, and Barbara McClintock showed us how irregular it is."