Watson and Crick: Standing On the Shoulders of Giants
... died. This results from dead S cells which transfer to living R cells. This material is referred to as the transforming principle. Avery furthered Griffith’s experimentation in the 1940s in his lab in Rocafeller University, NY. Avery was able to conduct the experiment in vitro, isolating the S strand and attempting to destroy it with protease. However, as protease is used to kill proteins, which was not the transforming principle, it therefore did not kill the bacteria; the mouse was injected and died. He discovered that if the transforming principle was treated, however, the mice survived the injection. Nuclease was used to destroy the DNA in the transforming principle, allowing the mice to live and at the same time proving DNA is the genetic material in living organisms. In 1948, Hershey and Chase conducted a similar experiment, but used the bacterial virus bacteriophage T2, or phage. As it was a virus, it was composed only of DNA and protein and needed the ribosomes of a host to produce protein to maintain existence. It was simple to work with this bacteria, as the genetic material had to be transferred to the host cell. The DNA consisted of phosphorus, but did not have sulfur, while the proteins consisted of sulfur, but were without phosphorus. Radioactive isotopes of each were used, so as to indicate location of materials. The point of this was to determine which of or if both of protein and DNA would transfer, thus revealing what true genetic material is. Phosphorous was only transferred and, therefore, Hershey and Chase were able to conclude that DNA is the sole genetic material in organisms. In the 1950s, Rosalind Franklin was one of the pioneering scientists to use X-ray diffraction, or X-ray crystallography. Thi...