AP Bio Study Guide

Big Idea 3.C

What are the lytic and lysogenic cycles of viruses?

In the lytic cycle, the phage enters a host cell, takes control of the cell machinery, replicates itself, and then causes the cell to burst, releasing a new generation of infectious phage viruses. These new viruses infect and kill thousands of cells in the same manner.

In the lysogenic cycle, viruses replicate without destroying the host cell. The phage virus becomes incorporated into a specific site in the host's DNA. When the host cell divides, the phage is replicated along with it, giving rise to a population of infected cell. At some point, an environmental trigger causes these prophages (dormant genes) to switch to the lytic phase.