The Phage Group was the intellectual medium where Watson became a working scientist. Importantly, the members of the Phage Group sensed that they were on the path to discovering the physical nature of the gene. In 1949, Watson took a course with Felix Haurowitz that included the conventional view of that time: that genes were proteins and able to replicate themselves. The other major molecular component of chromosomes, DNA, was widely considered to be a "stupid tetranucleotide," serving only a structural role to support the proteins. Even at this early time, Watson, under the influence of the Phage Group, was aware of the Avery–MacLeod–McCarty experiment, which suggested that DNA was the genetic molecule. Watson's research project involved using X-rays to inactivate bacterial viruses.