George Wells Beadle

1903-1989

American Geneticist

In 1958 George Wells Beadle shared the Nobel Prize in medicine with Joshua Lederberg (1925- ) and Edward Lawrie Tatum (1909-1975) for their discoveries that demonstrated the relationship between genes and the proteins they controlled. Beadle and Tatum demonstrated that genes act by regulating specific chemical events. Exploiting the potential of the bread mold Neurospora as a genetic and biochemical tool, they established the "one gene–one enzyme" theory.

Beadle was born in Wahoo, Nebraska, on a small family farm. One of his high school teachers recognized his potential and urged him to continue his education. He became interested in genetics while earning his bachelor's and master's degrees from the College of Agriculture of the University of Nebraska in 1926 and 1927, respectively. A professor of agronomy at Nebraska suggested that he continue graduate work with Rollins A. Emerson, an early advocate of Mendelian genetics and an eminent maize geneticist, at Cornell University. After earning his Ph.D. in 1931, Beadle worked as a postdoctoral fellow in the laboratory of Thomas Hunt Morgan (1866-1945) at the California Institute of Technology. He taught at Caltech for two years before spending a year in Paris researching the biochemical genetics of eye color mutations in Drosophila (fruit flies).

At the Institut de Biologie Physico-Chimique, he worked with Boris Ephrussi, who was trained in embryology and tissue culture and had studied Drosophila genetics in Morgan's laboratory. Working together, Beadle and Ephrussi analyzed the biochemical basis of heredity by studying how genes controlled the insects' eyecolor. Their tests with various eye color mutants proved that the steps involved in the sequential synthesis of eye-pigments were controlled by different genes.

Beadle became assistant professor of genetics at Harvard University in 1936, but moved to Stanford as professor of biology one year later. When Morgan died in 1945, Beadle became chairman of the Division of Biology at Caltech, where geneticists were moving from classical genetics to studies of the biochemistry of gene action. Classical genetics could address the question of how the gene was transmitted, but could not answer the question of how the gene worked or determine its chemical nature. Edward Tatum, a microbiologist and biochemist, joined Beadle to study the substances responsible for eye color in Drosophila.

Frustrated by the work with fruit flies, Beadle and Tatum decided that the bread mold Neurospora crassa would be more practical for studying the relationship between genes and the enzymes that controlled particular processes. Neurospora had a fairly short life cycle, techniques for genetic analysis had already been worked out, and its biochemical pathways were already well known. It was also easier to work with than the organisms that had traditionally been used by geneticists, and could be grown in a synthetic culture medium consisting of sugar, salts, and a simple growth factor (biotin).

Beadle and Tatum decided to reverse the procedures generally used to identify specific genes with particular chemical reactions. Instead of taking a mutant as their starting point and then searching for the chemical reaction it controlled, they decided to begin with known chemical reactions and look for the genes that controlled them. Mutations were induced by using x rays, then mutants that lost the ability to synthesize certain organic substances were selected. The induced mutations exhibited Mendelian patterns of inheritance. Biochemical and genetic analyses proved that the mutant strains were genetically different from the parental type.

When Beadle enunciated the "one gene–one enzyme" hypothesis in 1945, the chemical identity of the gene was still unknown. However, the work of Beadle and Tatum provided a valuable approach to discovering how genes work and became one of the foundations of modern genetics. Their success stimulated efforts to use simple organisms to solve fundamental questions about the nature of the gene.

LOIS N. MAGNER