Barbara McClintock

Barbara McClintock
(1902 - 1992)

American scientist whose discovery in the 1940s and '50s of mobile genetic elements, or "jumping genes," won her the Nobel Prize for Physiology or Medicine in 1983.
McClintock studied plant genetics at Cornell University in Ithaca, N.Y., receiving her doctorate in botany in 1927. While teaching at Cornell she helped show through her laboratory experiments that trait-determining (genetic) information is transferred between chromosomes in the crossing-over stage of cell division. Despite her pioneering work, she was unable to obtain a permanent academic position until 1941, when she joined the Cold Spring Harbor (N.Y.) Laboratory.

By observing and experimenting with variations in the coloration of kernels of corn (maize), McClintock discovered that genetic information is not stationary. By tracing pigmentation changes in maize and using a microscope to examine that plant's large chromosomes, she isolated two genes that she called "controlling elements." These genes controlled the genes that were actually responsible for pigmentation. McClintock found that the controlling elements could move along the chromosome to a different site, and that these changes affected the behaviour of neighbouring genes. She suggested that these transposable elements were responsible for new mutations in pigmentation or other characteristics.

The importance of her research was not recognized until the 1960s, when Francois Jacob and Jacques Monod discovered controlling elements in bacteria similar to those McClintock found in corn. McClintock won belated acclaim for her research, which significantly increased the knowledge of genetic function and organization.

BIBLIOGRAPHY.
McClintock's character and scientific contributions are explored by Evelyn Fox Keller, A Feeling for the Organism (1983).