Soiled bandages and a kitchen blender helped prove genes are made of DNA
In 1869 Friedrich Miescher scraped cells off pus-soaked bandages and found an odd phosphorus-rich substance he called nuclein. Decades later, Alfred Hershey and Martha Chase used an ordinary kitchen blender to show that this same material, DNA, carries the instructions viruses use to copy themselves. Humble kit, it turns out, cracked heredity open.
For much of the early twentieth century most scientists assumed proteins held genetic information; the very word protein was chosen to signal primary importance. The first crack came in 1928, when Frederick Griffith mixed dead virulent pneumococci with live harmless ones and found that the mixture killed his lab animals. Something had passed between the bacteria, a process now called transformation. At the Rockefeller Institute, Oswald Avery, Colin MacLeod and Maclyn McCarty spent years purifying that transforming principle and reported in February 1944 that it was DNA.
Hershey and Chase settled lingering doubts. They tagged viral protein coats with radioactive sulfur and viral DNA with radioactive phosphorus, let the viruses infect E. coli, then whirled the mixture in the blender to knock the empty shells off. The bacteria carried the phosphorus, so what the viruses had injected was DNA, not protein.
Structure followed. Erwin Chargaff showed in 1950 that the purine bases always match the pyrimidines in quantity. In 1953 Watson and Crick described the double helix, relying on Rosalind Franklin's X-ray data passed along by Maurice Wilkins and Max Perutz, and they shared the 1962 Nobel Prize with Wilkins. In 1958 Matthew Meselson and Franklin Stahl grew DNA with a heavy form of nitrogen and tracked it through rounds of copying, confirming that each new double helix keeps one old strand. Their work has been called the most beautiful experiment in biology.
By 1961 researchers had shown that genes are read three bases at a time, each non-overlapping triplet naming one amino acid. The discipline itself had been named only in 1945, by the English physicist William Astbury.
Source: Molecular biology
