DNA is the Genetic Material

Even with Griffith's and Avery's evidence in hand, a considerable number of biologists remained unconvinced that DNA was the genetic material. Their scepticism had a chemical basis: a typical eukaryotic chromosome contains roughly equal amounts of protein and DNA by mass, and proteins, being built from twenty different amino acids, seemed to offer far more structural and chemical variety than DNA, which is built from only four kinds of nucleotide. To many scientists of the time, only a molecule with that much chemical diversity seemed capable of encoding the enormous amount of information required to specify a living organism. This lingering doubt was only removed in 1952, when Alfred Hershey and Martha Chase performed a decisive experiment using bacterioph …