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.