In the lysogenic cycle of a bacteriophage, which statement correctly describes the state of the phage genome with respect to the bacterial host?
-
AA bacteriophage transfers bacterial DNA
-
BBacteria take up double-stranded DNA from the environment
-
CDNA-degrading enzymes in the extracellular medium would stop the process
-
DA bacteriophage genome is integrated into the bacterial genome
Answer
Correct Answer: A bacteriophage genome is integrated into the bacterial genome
Explanation
Introduction / Context:Lysogeny is a dormant relationship between a bacteriophage and its bacterial host. Instead of producing new virions immediately, the phage genome becomes a prophage integrated into the host chromosome and is replicated with the host. This concept underpins lysogenic conversion and prophage induction.
Given Data / Assumptions:
- We focus on the state of the phage genome during lysogeny.
- No lytic replication occurs during stable maintenance.
Concept / Approach:In lysogeny, integration is mediated by phage integrase and host recombination systems. A repressor protein keeps lytic genes inactive. Environmental stress (e.g., DNA damage) can trigger induction to the lytic cycle.
Step-by-Step Solution:
1) Identify that lysogeny ≠ active phage production.2) Recognize that the hallmark is chromosomal integration of the phage genome (prophage).3) Select the option describing integration into the bacterial genome.Verification / Alternative check:Lambda phage lysogeny model (cI repressor, att sites) is the classic proof.
Why Other Options Are Wrong:
- Phage transfers bacterial DNA: That is generalized or specialized transduction, not lysogeny itself.
- Bacteria take up dsDNA from environment: Transformation, not lysogeny.
- Extracellular DNases stop the process: Relevant to transformation, not to integrated prophage maintenance.
Common Pitfalls:
- Mixing up transduction (DNA transfer by phage particles) with the dormancy of lysogeny.
Final Answer:A bacteriophage genome is integrated into the bacterial genome