Barbara McClintock

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Barbara McClintock was born on June 16, 1902 in Hartford, Connecticut. She was the third child of Sara Handy McClintock and Thomas Henry McClintock, a physician.

After completing her high school education in New York City, she enrolled at Cornell University in 1919 and from this institution received the B.Sc degree in 1923, the M.A. in 1925, and the Ph.D. in 1927. She served as a graduate assistant in the Department of Botany for three years from 1924-27 and in 1927, following completion of her graduate studies, was employed as an Instructor, a post she held until 1931.

 

She was awarded a National Research Council Fellowship in 1931 and spent two years as a Fellow at the California Institute of Technology. After receiving the Guggenheimn Fellowship in 1933, she spent a year abroad at Freiburg.

 

She returned to the States and to the Department of Plant Breeding at Cornell the following year. McClintock left Cornell in 1936 to take the position of an Assistant Professorship in the Department of Botany at the University of Missouri. In 1941 she became a part of the Carnegie Institution of Washington, and began a happy and fruitful association which continued for the rest of her life.

 
In the 1940s, by observing and experimenting with variations in the coloration of kernels of corn, she discovered that genetic information is not stationary. By tracing pigmentation changes in corn 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. McClintock’s work was ahead of its time and was for many years considered too radical-or was simply ignored-by her fellow scientists.

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Deeply disappointed with her colleagues, she stopped publishing the results of her work and ceased giving lectures, though she continued doing research.

 

Not until the late 1960s and ’70s, after biologists had determined that the genetic material was DNA, did members of the scientific community begin to verify her early findings. When recognition finally came, McClintock was inundated with awards and honours, most notably the 1983 Nobel Prize for Physiology or Medicine.

 
In Berlin, she befriended Richard Goldschmidt, another notoriously prickly personality. Goldschmidt introduced her to the group of German geneticists who were exploring the physiology of the gene, cytoplasmic inheritance, and the relation of genes to embryological development.

 

When Berlin, the capital of the Nazi state, grew too depressing for McClintock, he arranged for her to escape to Freiburg, where she worked in the laboratory of Friedrich Oehlkers, another member of the group.

 

As Jan Sapp showed in his Beyond the Gene (1987), a central concern of this school was the “paradox of nuclear equivalence”: if, as everyone assumed, a gene is “on” all the time, and if each cell contains all the genes, how do different cell types arise? How do development and differentiation occur? The Germans’ answer was that some regulatory machinery must lie outside the nucleus, in the cytoplasm.

 

McClintock returned early from Germany, but only after absorbing an interest in gene regulation that remained for the rest of her life.