Hermann J. Muller

Hermann Joseph Muller (1890–1967) was a member of Thomas Hunt Morgan's famous 'Fly Room' at Columbia University, helping map chromosomes in Drosophila melanogaster. In 1926 at the University of Texas at Austin, Muller exposed male fruit flies to heavy doses of X-rays.

Breeding the irradiated flies using a balancer chromosome method (ClB technique), Muller proved that X-rays increased the frequency of lethal genetic mutations by 15,000 percent, demonstrating that genes are physical molecules vulnerable to ionizing radiation. Awarded the Nobel Prize in 1946, he signed the Russell-Einstein Manifesto warning of nuclear destruction.