Introduction

Abstract

Viruses have occupied a central position in molecular biology ever since its development as an independent discipline. Indeed, molecular biology itself largely developed out of the pioneer studies of Delbrück, Luria and Hershey, who realized, in the late 1930’s, that bacterial viruses (bacteriophages, often abbreviated to phages) had properties which made them uniquely suitable as a model system for an attack on one of the then outstanding problems of biology, the definition of the gene in physical and chemical terms. The favourable properties of these viruses include the rapidity of their growth, their ease of assay, and the availability of easily scored genetic markers. Taken together, this means that quantitative genetic experiments can be done very quickly. The small size of viruses also suggested that their structure would be simple, which, in turn, led to the belief that this kind of system would be suitable for biochemical and physiological studies.