George Beadle

George Wells Beadle (October 22, 1903 – June 9, 1989) was an American geneticist.

In 1926 he earned his Bachelor of Science degree at the University of Nebraska and subsequently worked for a year with Professor F.D. Keim, who was studying hybrid wheat.

In 1927 he earned his Master of Science degree, and Professor Keim secured for him a post as Teaching Assistant at Cornell University, where he worked, until 1931, with Professors R.A. Emerson and L.W. Sharp on Mendelian asynapsis in Zea mays.

For this work he obtained, in 1931, his Doctor of Philosophy degree.

In 1931 Fellowship at the California Institute of Technology at Pasadena, where he remained from 1931 until 1936.

During this period he continued his work on Indian corn and began, in collaboration with Professors Theodosius Dobzhansky, S. Emerson, and Alfred Sturtevant, work on crossing-over in the fruit fly, Drosophila melanogaster.

In 1935 Beadle visited Paris for six months to work with Professor Boris Ephrussi at the Institut de Biologie physico-chimique.

In 1936 Beadle left the California Institute of Technology to become Assistant Professor of Genetics at Harvard University.

A year later he was appointed Professor of Biology (Genetics) at Stanford University and there he remained for nine years, working for most of this period in collaboration with Tatum.

This work of Beadle and Tatum led to an important generalization.

This was that most mutants unable to grow on minimal medium, but able to grow on “complete” medium, each require addition of only one particular supplement for growth on minimal medium.

If the synthesis of a particular nutrient (such as an amino acid or vitamin) was disrupted by mutation, that mutant strain could be grown by adding the necessary nutrient to the minimal medium.

This finding suggested that most mutations affected only a single metabolic pathway.

Further evidence obtained soon after the initial findings tended to show that generally only a single step in the pathway is blocked.

Following their first report of three such auxotroph mutants in 1941, Beadle and Tatum used this method to create series of related mutants and determined the order in which amino acids and some other metabolites were synthesized in several metabolic pathways.

The obvious inference from these experiments was that each gene mutation affects the activity of a single enzyme.

This led directly to the one gene-one enzyme hypothesis, which, with certain qualifications and refinements, has remained essentially valid to the present day.

As recalled by Horowitz, the work of Beadle and Tatum also demonstrated that genes have an essential role in biosynthesis.

At the time of the experiments (1941), non-geneticists still generally believed that genes governed only trivial biological traits, such as eye color, and bristle arrangement in fruit flies, while basic biochemistry was determined in the cytoplasm by unknown processes.

Also, many respected geneticists thought that gene action was far too complicated to be resolved by any simple experiment.

Thus Beadle and Tatum brought about a fundamental revolution in our understanding of genetics.

In 1946 Beadle returned to the California Institute of Technology as Professor of Biology and Chairman of the Division of Biology.

In 1958 he shared one-half of the Nobel Prize in Physiology or Medicine with Edward Tatum for their discovery of the role of genes in regulating biochemical events within cells.

He also served as the 7th President of the University of Chicago.

Beadle and Tatum's key experiments involved exposing the bread mold Neurospora crassa to x-rays, causing mutations.

In a series of experiments, they showed that these mutations caused changes in specific enzymes involved in metabolic pathways.

These experiments led them to propose a direct link between genes and enzymatic reactions, known as the One gene-one enzyme hypothesis.

George Wells Beadle was born in Wahoo, Nebraska.

He was the son of Chauncey Elmer Beadle and Hattie Albro, who owned and operated a 40 acre farm nearby.

George was educated at the Wahoo High School and might himself have become a farmer if one of his teachers at school had not directed his mind towards science and persuaded him to go to the College of Agriculture in Lincoln, Nebraska.

Together they began the study of the development of eye pigment in Drosophila which later led to the work on the biochemistry of the genetics of the fungus Neurospora for which Beadle and Edward Lawrie Tatum were together awarded the 1958 Nobel Prize for Physiology or Medicine.

Here he remained until January 1961 when he was elected Chancellor of the University of Chicago and, in the autumn of the same year, President of this University.

After retiring, Beadle undertook a remarkable experiment in maize genetics.

In several laboratories he grew a series of Teosinte/Maize crosses.

Then he crossed these progeny with each other.

He looked for the rate of appearance of parent phenotypes among this second generation.

The vast majority of these plants were intermediate between maize and Teosinte in their features, but about 1 in 500 of the plants were identical to either the parent maize or the parent teosinte.

Using the mathematics of Mendelian genetics, he calculated that this showed a difference between maize and teosinte of about 5 or 6 genetic loci.

This demonstration was so compelling that most scientists now agree that Teosinte is the wild progenitor of maize.

During his career, Beadle has received many honors.