Born in Breslau. MD from the University of Breslau in 1933. Soon left for Scotland and finished his PhD at the University of Edinburgh (1936). After completing his doctorate he emigrated to the USA. He worked at a number of institutes before joining the faculty at the University of California, Berkeley in 1952 where he remained until his death.
His most noted research was on the tobacco mosaic virus. He discovered that the genetic control of viral reproduction was RNA and that it is carried in the nucleic core of each virus. In 1955 he and biophysicist Robley Williams showed that a functional virus could be created out of purified RNA and a protein coat. In 1960 he announced the complete sequencing of the 158 amino acids in the virus.