Question

Which of the following leads to the destruction of the host cells?

• A. Lysogenic cycle
• B. Lytic cycle
• C. Prophage
• D. Temperate phase

Hint:

To distinguish the two main phage cycles:
- Lytic = Lysis (cell bursts, host is destroyed).
- Lysogenic = Lysogeny (integration, silent replication, host survives).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Bacteriophages (viruses that infect bacteria) can undergo two alternative lifecycles within their host cells: the lytic cycle and the lysogenic cycle.

Step 2: Detailed Explanation:
- Lytic Cycle (B): This is the active, productive phase of viral replication.
The phage injects its DNA into the bacterial host, hijacks the host's transcription and translation machinery to synthesize viral proteins, and replicates its genome.
Once new phage particles are assembled, the phage encodes enzymes (such as lysins and holins) that degrade the bacterial cell wall.
This causes the host cell to rupture (lyse), releasing hundreds of progeny virions and resulting in the immediate destruction of the host cell.
- Lysogenic Cycle (A): In this cycle, the viral genome integrates into the host chromosome, becoming a dormant Prophage (C).
The host cell survives and replicates normally, copying the viral DNA along with its own.
- Temperate phase (D) refers to phages capable of choosing between lytic and lysogenic pathways, but the lytic cycle is the specific process that destroys the host cell.

Step 3: Final Answer:
The lytic cycle leads to the destruction of the host cells.