Hershey spent the first 16 years of his career as an instructor in bacteriology at Washington University, St Louis. The head of the department was Bronfenbrenner who, like many people in those days, believed that viruses were proteins that somehow triggered their host cell into making more of the same so were not in any sense alive. Bronfenbrenner's influence ensured that Hershey's early publications (on bacterial growth and virus-antibody interactions) were rather undistinguished. Certainly, they gave no hint of what was to come.
But in 1943 Hershey met Max Delbrück, just at the time when Delbrück and Salvador Luria were struggling with the mathematics of mutation in bacteria. Three years later, at the age of 38, Hershey reported that bacterial viruses contain genetic determinants which occasionally undergo spontaneous, inheritable changes (mutation). Shortly afterwards, he showed that these determinants display genetic linkage and form linear arrays — just like the chromosomal genes of higher organisms. This established that bacterial viruses are a simple version of all living creatures and, as Delbrück had imagined, that they could be used to investigate the nature of the gene.
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