Hermann Joseph Muller

Hermann Joseph Muller was an American geneticist who demonstrated that exposing an organism to X-ray radiation could induce heritable genetic mutations, establishing for the first time a measurable, quantitative link between an environmental agent and the mutation rate. In a series of experiments culminating in a landmark 1926 report, Muller irradiated fruit flies with X-rays and showed a clear, dose-dependent relationship between radiation exposure and the frequency of lethal mutations, work that also gave geneticists a practical new method for generating large numbers of mutations to study. Based on this research Muller argued that there was no safe threshold of radiation exposure below which mutations would not occur, a linear no-threshold model of radiation risk that influenced subsequent radiation protection policy. He was awarded the 1946 Nobel Prize in Physiology or Medicine for the discovery of the production of mutations by means of X-ray irradiation. Muller trained under Thomas Hunt Morgan, held positions at Rice University, the University of Texas and Indiana University, spent eight years working in Europe including in the Soviet Union during the 1930s, and later became a prominent public advocate against atmospheric nuclear weapons testing, signing the 1955 Russell-Einstein Manifesto.