Oswald Avery

Oswald Avery was born in Halifax, Nova Scotia, to a Baptist minister and his wife, and moved to New York City as a child. He studied medicine at Columbia University, graduating in 1904, and initially practiced as a physician before turning to bacteriology and immunology. In 1913, he joined the Rockefeller Institute for Medical Research, where he spent most of his career, focusing on the chemical basis of immunity and the pneumococcus bacterium.

In 1928, Frederick Griffith had shown that heat-killed virulent pneumococci could transform a non-virulent strain into a virulent one, but the nature of the 'transforming principle' was unknown. Avery, with MacLeod and McCarty, systematically purified the active substance from the heat-killed bacteria and showed that it was DNA, not protein, by demonstrating that the transforming activity was destroyed by DNase but not by proteases or RNase. Their 1944 paper in the Journal of Experimental Medicine concluded that DNA is the substance that carries hereditary information, a conclusion that initially met with skepticism but was later confirmed by the Hershey–Chase experiment in 1952.²

Avery's discovery was pivotal in establishing DNA as the genetic material, directly influencing James Watson and Francis Crick's later elucidation of the double helix. He received numerous honors, including the Copley Medal in 1944 and the Lasker Award in 1947, but never won a Nobel Prize, a fact often attributed to the Nobel Committee's conservative view of his work. The Avery–MacLeod–McCarty experiment is now a cornerstone of molecular biology, and Avery's name is commemorated in the Avery–MacLeod–McCarty Award for outstanding research in molecular genetics.

Beyond the famous experiment, Avery made significant contributions to immunochemistry, including the classification of pneumococcal types and the discovery of the capsular polysaccharide that determines virulence. He was known for his meticulous laboratory technique and his reluctance to publish prematurely, which delayed the 1944 paper by several years. Avery also mentored many young scientists, including René Dubos, who later became a prominent environmentalist. His personal papers are archived at the Rockefeller University, offering insight into his cautious and collaborative approach to science.

Transformation

The genetic alteration of a cell resulting from the uptake of exogenous DNA.

DNase

An enzyme that degrades DNA.

Hershey–Chase experiment

A 1952 experiment that confirmed DNA as the genetic material using bacteriophages.