The DNA Double Helix

An Alternative History of the Discovery of the Structure of DNA. James Watson Started college at the age of 15 and had completed his PhD research at the age of 23. While an undergraduate he shifted his interest from ornithology to molecular biology. Large parts of Biology was making a transition from the era of classical biology to the new age of molecular biology. Watson faced the challenge of trying to get a chance to join a research laboratory that would bring him closer to his goal of learning the physical basis of heredity. A number of scientific specialties were converging on this goal: genetics, biochemistry, biophysics. Watson’s PhD research involved a genetic approach, making use of physical techniques to probe the properties of viruses. The viruses he worked with were the smallest known genetic agents that some thought of as comprising “naked genes”. For his post-doctoral research, Watson moved on to join a laboratory in Europe that studied the chemical components of DNA and the chemistry of nucleic acids. Another major approach to DNA, X-ray diffraction studies, he would soon learn about. Just before leaving for Europe and his post-doctoral research, Watson spent time at the Cold Spring Harbor laboratories on Long Island, New York. Watson learned about experiments being attempted to determine the identity of the molecule that carried genetic instructions. The choices had been narrowed to protein and DNA. The type of virus Watson had studied contained both protein and DNA. In the late 1940, at the start of the nuclear age, radioactive isotopes were starting to be used as probes of biological molecules. DNA contains phosphorus while protein contains sulfur. Attempts were being made to label the components of viruses and determine which one was inserted into infected cells in order to carry the viral genes inside where they could instruct the infected cell to make new viruses.