Phage gene expression timing — Which protein sets are typically synthesized from late mRNA during a lytic infection?
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APhage structural proteins
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BProteins that aid assembly but are not part of the virion (scaffolds/chaperones)
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CProteins for host cell lysis and phage release
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DAll of the above
Answer
Correct Answer: All of the above
Explanation
Introduction / Context:Lytic phage infections proceed through an ordered transcriptional program: early genes for takeover and replication functions, and late genes for particle construction and release. Knowing which proteins appear from late mRNA clarifies phage biology and biotechnology applications.
Given Data / Assumptions:
- Late gene expression follows genome replication.
- Late mRNAs encode virion components and lysis machinery.
- Some late proteins assist assembly but are not retained in the mature virion.
Concept / Approach:From late mRNA, phages synthesize capsid and tail proteins (structural), assembly-helper proteins (scaffolding, chaperones), and lysis proteins (e.g., endolysins, holins) that mediate host cell rupture. Therefore, all listed categories are produced from late transcripts.
Step-by-Step Solution:
Recall early vs. late gene roles.Map late mRNA to structural, assembly, and lysis functions.Select “All of the above.”Verification / Alternative check:Well-characterized phages (e.g., T4) show this transcriptional order; late promoters drive structural and lysis genes.
Why Other Options Are Wrong:
- Picking only one subset ignores the full scope of late-phase products.
Common Pitfalls:Assuming lysis proteins are early; they are typically expressed late to time particle release.
Final Answer:All of the above