Karl Günter Zimmer was a German physicist and radiation biologist, known for his work on the effects of ionizing radiation on DNA.
In 1935, he published the major work, Über die Natur der Genmutation und der Genstruktur, with N. V. Timofeev-Resovskij, and Max Delbrück; it was considered to be a major advance in understanding the nature of gene mutation and gene structure. In 1945, he was sent to the Soviet Union to work on their atomic bomb project.
In 1955, he left Russia and eventually went to West Germany.
