Concept 18 Bacteria and viruses have DNA too.

Joshua Lederberg Alfred Hershey Joshua Lederberg discovered bacterial recombination and started a new field of research. Alfred Hershey was a phage geneticist who, with his research assistant, Martha Chase, did one of the most famous experiments in molecular biology. The "blender" experiment proved that DNA carried genetic information.

Alfred Day Hershey (1908-1997)

Alfred Hershey

Alfred Hershey was born in Owosso, Michigan. He graduated from Michigan State in 1930 with a B.S., and in 1934 with a Ph.D. After his Ph.D., Hershey accepted a position at the Washington University School of Medicine in the Department of Bacteriology, where he started working on bacteriophage.

At the time, there weren't many people working on bacteriophage. Two other scientists who read Hershey's papers, Max Delbrück and Salvador Luria, were collaborating on experiments using bacteriophage. In 1943, Delbrück invited Hershey to Nashville to visit his lab. In 1946, working with Delbruck, Hershey discovered that phage can recombine when co-infected into a bacteria host. This led to a new area of phage genetics.

As leading researchers in the field of bacteriophage, Delbrück, Luria, and Hershey established the American Phage Group which had a tremendous influence on bacteriophage research.

Hershey stayed at the Washington University School of Medicine until 1950. He then accepted a position from the Carnegie Institution of Washington's Department of Genetics at Cold Spring Harbor. Here he and Martha Chase did the Hershey-Chase blender experiment that proved that phage DNA, and not protein, was the genetic material. For this, and his body of work on bacteriophage, Hershey shared the 1969 Nobel Prize for Physiology or Medicine with Max Delbrück and Salvador Luria.

In 1962, Hershey became the Director of the Genetics Research Unit at Cold Spring Harbor Laboratory. His lab continued to work on bacteriophage, focusing on phage recombination and genetics. In 1974, Hershey retired, though he was still a regular visitor to Cold Spring Harbor Laboratory. In 1979, a building on the grounds was dedicated to him.

Hershey was known to be an excellent writer and editor. His papers were clear and concise and he helped other scientists learn the craft of scientific writing. He enjoyed gardening and woodworking, as well as classical music. In the early 80s, he became interested in computers and used them to catalog his classical music collection. He was busy, active, and still learning even in retirement.

factoid Did you know ?

Joshua Lederberg was Edward Tatum's graduate student. Lederberg's wife Esther was George Beadle's graduate student.


Conjugation occurs only if bacteria are in close contact. Can you design an experiment that shows this is true?