Lysogenic cycle

Definition

The lysogenic cycle is a method of viral replication in which a virus integrates its genetic material into the host cell's DNA, allowing it to be replicated along with the host's genome without immediately destroying the host. This cycle can remain dormant for extended periods, with the viral DNA, called a prophage, being passed on to daughter cells during cell division. The lysogenic cycle is distinct from the lytic cycle, where the virus replicates and causes immediate cell death.

5 Must Know Facts For Your Next Test

1. In the lysogenic cycle, viral DNA can remain dormant for years before being activated to enter the lytic cycle.
2. The integration of viral DNA into the host genome can provide advantages such as immunity to superinfection by similar viruses.
3. Environmental factors like stress or UV light can trigger the switch from lysogenic to lytic cycle in some viruses.
4. Lysogenic viruses are often less harmful to their hosts in the short term compared to lytic viruses since they do not immediately kill host cells.
5. Many bacteriophages utilize the lysogenic cycle as a survival strategy, allowing them to persist in a population without causing immediate harm.

Review Questions

• How does the lysogenic cycle differ from the lytic cycle in terms of viral replication and impact on host cells?
  • The main difference between the lysogenic and lytic cycles lies in their effects on host cells. In the lysogenic cycle, viral DNA integrates into the host's genome and remains dormant, allowing it to replicate with the host without killing it. In contrast, the lytic cycle involves the active replication of the virus and culminates in cell lysis, leading to immediate death of the host cell. This means that lysogenic viruses can coexist with their hosts for longer periods without causing harm.
• What role do environmental factors play in determining whether a virus will follow the lysogenic or lytic cycle?
  • Environmental factors such as stress, nutrient availability, or exposure to UV light can influence a virus's decision to enter either the lysogenic or lytic cycle. Under favorable conditions, a virus may choose the lysogenic cycle, integrating into the host's DNA and ensuring its survival over time. However, adverse conditions may trigger activation of the viral genome from its dormant state, prompting a shift to the lytic cycle where it actively replicates and ultimately destroys its host.
• Evaluate how the lysogenic cycle contributes to genetic diversity within bacterial populations and its implications for evolution.
  • The lysogenic cycle plays a significant role in genetic diversity within bacterial populations by facilitating horizontal gene transfer through prophage integration. When a temperate phage integrates its DNA into a bacterial genome, it can carry new genes that confer beneficial traits such as antibiotic resistance or metabolic capabilities. As these traits are passed on during bacterial cell division, they enhance genetic variation and adaptability within populations. This process contributes to evolutionary dynamics by allowing bacteria to acquire new functionalities that can improve their survival in changing environments.

Related terms

prophage: A prophage is the integrated form of a bacteriophage's DNA within a bacterial host's genome during the lysogenic cycle.

lytic cycle:

The lytic cycle is a viral replication process that results in the destruction of the host cell and the release of new viral particles.

temperate phage: A temperate phage is a type of bacteriophage that can enter either the lysogenic or lytic cycle, depending on environmental conditions.