Final answer:
The development of Bacteriophage λ involves a choice between lytic and lysogenic cycles, where gene expression is regulated in response to environmental cues, leading to either the production of new viruses or dormancy via integration into the host genome.
Step-by-step explanation:
The cascade of gene expression during the development of Bacteriophage λ dictates whether the virus will enter a lytic or lysogenic cycle after infecting a bacterium. Upon attaching to and penetrating a bacterial host cell, the linear-double stranded DNA of the phage with cohesive ends forms a circular molecule. In the early phase, the phage can choose lytic phase, where it hijacks the host's machinery to produce viral components and eventually lyses the host releasing new viruses; or the lysogenic phase, where the phage DNA integrates into the host genome as a prophage. Environmental factors such as starvation or exposure to toxins can trigger a prophage to excise from the bacterial chromosome and switch to the lytic pathway.