Posted by: Glow-worm PJ3 JUN 2014
The Nobel prize winning geneticist George Wells Beadle died 25 years ago on 9 June 1989.
Born on 22 October 1903, in Wahoo, Nebraska, he graduated from the University of Nebraska in 1926 and began working on the genetics of wheat, for which he was awarded his PhD in 1931.
In 1937, he teamed up with Edward Tatum to research the hypothesis that one gene was responsible for the production of one protein. They switched from studying the fruit fly Drosophila melanogaster to the fungus Neurospora, whose simpler genetic make-up made it easier to study the actions of individual genes.
Samples of the fungus were irradiated in order to produce genetic mutations which, if Beadle’s theory was correct, would affect the function of enzyme systems, with biologically quantifiable effects. Biotin is the only external vitamin normally required by Neurospora, but they discovered that mutant strains developed with special nutritional needs, in that they could not survive without the addition of thiamine and choline. They also measured a build-up of substrates, unable to be converted due to the missing enzymes. Analysis showed that each mutant differed by just one gene, which led them to the one gene, one enzyme hypothesis. This suggested that each gene is responsible for the synthesis of a specific enzyme, a hypothesis that has subsequently been refined, in that it has been shown that genes code for individual polypeptides, several of which can form complex proteins, for example haemoglobin, so that a more accurate description of the theory may be one gene, one polypeptide. The pair were awarded the Nobel prize for their work in 1958.
Even after retirement, Beadle continued his experiments, conducting some remarkable work on the genetics of cultivated maize, proving by a combination of cross-breeding and Mendelian statistical analysis, that modern-day maize had been developed from teosinte, a wild Mexican grass.