Oswald Avery: Discovering DNA as Responsible for Passing Hereditary Information

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There have been many Eureka moments in the history of genetics. As with most discoveries they’re achieved by building on what’s gone on before; the discoveries, ideas and concepts formed by previous generations of scientists. As Sir Isaac Newton wrote to his rival Robert Hooke, “If I have seen further it is by standing on the shoulders of giants.”

Crick and Watson’s groundbreaking research in working out the structure of DNA was also made possible by ‘standing on the shoulders of giants.’ One of those was Oswald Avery.

Who was Oswald Avery?

Oswald Avery (1877-1955) was one of the pioneers of the scientific discipline of immunochemistry, spending most of his time working out of the Rockefeller Institute. His career was long and distinguished, but what marks him out as a truly great figure in the history of genetics was his landmark paper in 1944 which laid the foundation for much of the genetics revolution that followed. In it Oswald described genes and chromosomes as being made up of DNA, and that this DNA was the hereditary material, or so called “transforming principle” that was responsible for the passing down of traits from one generation to the next. This work was only made possible by the foundations laid by previous researchers, such as Frederick Miescher, the man who discovered DNA in 1869.

It perhaps seems difficult for us to understand just how much of a big deal Avery’s paper was, and it certainly met with some scepticism at the time. But up until this moment in the 1940’s the prevailing notion was that the hereditary information would be found in proteins, as DNA was deemed to be too simple a substance.

“If we are right, and of course that is not yet proven, then it means that nucleic acids are not merely structurally important but functionally active substances in determining the biochemical activities and specific characteristics of cells and that by means of a known chemical substance it is possible to induce predictable and hereditary changes in cells. This is something that has long been the dream of geneticists.” (Oswald. T. Avery, 1943).

Oswald’s Big Moment

Oswald Avery’s big moment in the history of genetics came when he was working on strains of pneumococci bacteria. Two strains were used; the R strain (harmless) and the S strain (causes pneumonia). The work was based on knowledge that a bacterium is able to transform another bacterium by passing genetic material through a medium. Avery’s challenge, along with his colleagues Colin MacLeod and MacLyn McCarty, was to show that this transforming factor, or transforming principle as it was called, was DNA.

Their work was prompted by the 1928 discovery of Frederick Griffith that mice inoculated with dead encapsulated pneumococci and live harmless encapsulated pneumococci still got pneumonia. Yet how could this be possible when the lethal strain had been killed? How the harmless bacteria had been transformed was something of a mystery.

Avery’s research concept was elegant in its simplicity, though it took many years to perfect the techniques to be able to do it. Simply put live harmless bacteria next to dead lethal strains, strip away various cellular components to see which ones are responsible for turning a harmless strain into a lethal one. When proteins were taken out of the equation, the harmless bacteria were still transformed. When DNA was taken out, there weren’t any transformations. They isolated the nucleic acid and showed that it was responsible for the transformation, the passing of hereditary information.

It was a momentous discovery, though you wouldn’t have guessed that if you read the tile of his landmark paper; “Studies on the chemical nature of the substance inducing transformation of pneumococcal types.” Nonetheless it helped to start the genetics revolution that was to come, in particular the work of Crick and Watson in determining the structure of DNA.

Source of quote

National Library of Medicine


Further reading

The man who discovered DNA