How are the iysogenic and lytic cycles different?

The lysogenic cycle describes a symbiotic relationship between some viruses (called temperate viruses) and their hosts. Here are the key differences between the lysogenic and lytic cycles:

1. Integration vs. Replication:

- Lysogenic Cycle: After infecting the host cell, the viral DNA integrates into the host's chromosomal DNA, becoming a prophage or provirus. The integrated viral DNA is replicated alongside the host DNA during cell division.

- Lytic Cycle: In the lytic cycle, the viral DNA or RNA replicates independently within the host cell, creating multiple copies of itself.

2. Host Survival:

- Lysogenic Cycle: The lysogenic cycle allows the host cell to survive and continue its normal functions. The prophage can remain dormant within the host for an extended period, potentially for generations.

- Lytic Cycle: The lytic cycle results in the destruction of the host cell. After viral replication and assembly, the newly formed viruses burst open (lyse) the host cell, releasing the viral particles into the environment.

3. Transmission:

- Lysogenic Cycle: The prophage can be transmitted vertically to the host cell's progeny during cell division. Each daughter cell will carry a copy of the integrated viral DNA.

- Lytic Cycle: The progeny viruses produced in the lytic cycle are released from the host cell and can infect other susceptible host cells.

4. Induction and Prophage Activation:

- Lysogenic Cycle: Under specific conditions, the prophage can be induced to exit the dormant state and enter the lytic cycle through a process called prophage induction. Various triggers, such as environmental stressors or host defense mechanisms, can initiate induction.

- Lytic Cycle: In the lytic cycle, the viral DNA is continuously replicated and transcribed, leading to the production of viral components and ultimately the lysis of the host cell.

5. Immunity:

- Lysogenic Cycle: Lysogenized host cells gain immunity against superinfection by the same or closely related viruses due to the presence of the integrated prophage. This protection is known as superinfection immunity.

- Lytic Cycle: The lytic cycle does not provide immunity to the host cell. Once infected, the host cell undergoes lysis, releasing viral particles that can infect other cells.

It's important to note that the lysogenic and lytic cycles are not mutually exclusive. Some viruses can switch between these two life cycles depending on environmental or internal factors. The balance between these cycles plays a significant role in viral persistence, diversity, and the host's response to infection.