Question

A bacteriophage genome integrated into the circular bacterial chromosome is known as

• A. Prophage
• B. Metaphage
• C. Bacphage
• D. Prophase

Hint:

A prophage represents the latent stage of a temperate phage in the lysogenic cycle, where the viral DNA is integrated into and replicates with the host bacterial chromosome.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Temperate bacteriophages can undergo two alternative life cycles: the lytic cycle (which leads to host cell lysis) and the lysogenic cycle (where the phage genome replicates silently alongside the host).

Step 2: Detailed Explanation:
When a temperate bacteriophage (such as Phage \(\lambda\)) infects a host bacterium, its double-stranded DNA can integrate into a specific site on the host's circular chromosome via site-specific recombination.
This integrated, latent form of the viral genome is called a prophage.
While in the prophage state, the viral genes that code for lytic functions are repressed by a phage-encoded repressor protein.
The prophage replicates passively alongside the host chromosome during cell division, transmitting the viral genome to all subsequent generation of daughter cells without harming the host.
If the host cell experiences stress or DNA damage (such as UV radiation), the repressor protein is cleaved, inducing the prophage to excise from the host chromosome and enter the lytic cycle.
In contrast:
- Prophase is the first stage of eukaryotic mitosis or meiosis.
- Metaphage and Bacphage are not standard biological terms used to describe integrated viral genomes.

Step 3: Final Answer:
Thus, the integrated bacteriophage genome is called a prophage.