Joshua Lederberg


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US geneticist who discovered genetic recombination in bacteria, for which he received the 1958 Nobel Prize for Physiology or Medicine.

Born in Montclair, New Jersey, Lederberg graduated in 1944 from Columbia College and in 1946 joined Edward Tatum at Yale University. Here they discovered that a mixture of two mutant strains of the bacterium Escherichia coli produced limited numbers of normal (wild-type) individuals. By a process called conjugation, DNA was transferred through minute hairlike structures (pili) from one individual to another, a form of sexual reproduction. Lederberg received his PhD in 1948 and was appointed assistant professor of genetics at Wisconsin University, becoming associate professor in 1950 and professor in 1954. In 1952 he published his discovery of transduction in the bacterium Salmonella typhimurium. A virus (bacteriophage P22) infective to the bacterium incorporated part of the bacterial chromosome into its outer coat and transferred this to another individual bacterium. These findings contributed much to understanding the mechanisms of recombination in DNA that are crucial to genetic engineering.

In 1959 Lederberg was appointed professor of genetics at Stanford University's newly founded department. He was president of Rockefeller University, New York, (1978–1990). He received the US National Medal of Science in 1989.

Subjects: Science and Mathematics.

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