Hermann Joseph Muller
The Nobel Prize in Physiology or Medicine 1946
Born: 21 December 1890, New York, NY, USA
Died: 5 April 1967, Indianapolis, IN, USA
Affiliation at the time of the award: Indiana University, Bloomington, IN, USA
Prize motivation: "for the discovery of the production of mutations by means of X-ray irradiation."
Prize share: 1/1
In order to explain how organisms' genes can change, allowing species to evolve and new species to arise, a new term was coined in the late 1880s - "mutation". Mutation involves sudden changes in an organism's genetic code. Herman Muller studied the hereditary characteristics of fruit flies and, in 1927, discovered that the number of genetic mutations observed in fruit flies increased when they were exposed to x-rays. He found that the higher the dose of x-rays and other ionizing radiation the flies were exposed to, the greater the number of mutations that occurred.