How would mutations that inactivate each of the following genes affect the determination of the lytic or lysogenic life cycle in mutated λ phage strains? Explain your answers. cII

Key Concepts

Lytic and Lysogenic Cycles

The lytic and lysogenic cycles are two distinct pathways that bacteriophages, like λ phage, can follow after infecting a host bacterium. In the lytic cycle, the phage replicates rapidly, leading to the destruction of the host cell and the release of new phage particles. In contrast, the lysogenic cycle involves the integration of the phage DNA into the host genome, allowing it to replicate along with the host cell without causing immediate harm.

cII Gene Function

The cII gene of λ phage plays a crucial role in determining the switch between the lytic and lysogenic cycles. It encodes a protein that stabilizes the expression of genes necessary for lysogeny, promoting the integration of phage DNA into the host genome. When cII is active, it favors the lysogenic pathway; however, mutations that inactivate cII can lead to a preference for the lytic cycle, as the regulatory balance shifts.

Mutations and Gene Inactivation

Mutations are changes in the DNA sequence that can lead to the inactivation of genes, affecting the function of the proteins they encode. In the context of the cII gene, mutations that disrupt its function can alter the decision-making process of the phage regarding its life cycle. Understanding how specific mutations impact gene function is essential for predicting the behavior of mutated λ phage strains in terms of their lytic or lysogenic tendencies.