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Every graduate student has been quizzed at least once on the life cycle and genetics of the bacterial phage lambda. This virus is perhaps the most well-characterized piece of genetic information in all of biology. Over the years, lambda has served mainly as a dependable laboratory workhorse for everyday molecular biology experiments. This bacterial virus is well suited for cloning purposes and can propagate complex mixtures of exogenous DNA of a convenient size. For genetic experimentation, sophisticated assays of gene and protein function have been designed based on the molecular components of the virion. The protein components of lambda gene regulation and their interactions are known at the most detailed level. In fact, many of these proteins have been examined at the atomic level through x-ray crystallography. Investigators can use their molecular knowledge of lambda to design experiments that manipulate the regulatory circuits in ways that produce defined results.
The lambda life cycle consists of two distinct phases, lytic and lysogenic. The lytic phase is characterized by infection of a bacterial host followed by intense phage replication and the production of a large number of progeny. Released virions infect adjacent cells...