In 1956 he discovered the enzyme DNA-polymerase, which enabled molecules
of the genetic material DNA to be synthesized for the first time. For this
work he shared the 1959 Nobel Prize for Physiology or Medicine. By 1967
he had synthesized a biologically active artificial viral DNA.
Kornberg was born in New York and studied at the University of Rochester School of Medicine. He held senior appointments at the Washington University School of Medicine (1953) and the Stamford University School of Medicine, Palo Alto, California (1959), before becoming head of the Biochemistry Department at Stamford.
In 1957, Kornberg made an artificial DNA, but this turned out to lack genetic activity. He then tried to make a simpler one, the DNA of a virus known as Phi X174, which is single-stranded and in the form of a ring; its activity (infectivity) is lost if the ring is broken. In 1966 he discovered the enzyme needed to close the ring. When the synthetic DNA was added to a culture of bacteria cells, the cells abandoned their normal activity and started to produce Phi X174 viruses.