Question

Virus replication inside the susceptible host takes place in different steps as below. Arrange these steps as per the order they occur.
(A). Synthesis of structural proteins
(B). Assembly, maturation and release of virus
(C). Attachment, penetration and uncoating
(D). Synthesis of mRNA and functional proteins
Choose the correct answer from the options given below:

• A. (C), (D), (A), (B).
• B. (B), (A), (D), (C).
• C. (B), (D), (A), (C).
• D. (C), (B), (D), (A).

Hint:

Remember:
- Non-structural/functional proteins are synthesized *early* to replicate the genome.
- Structural capsid proteins are synthesized *late* to package the genome.
- Release is always the absolute final step.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
This question deals with general virology, specifically the standard sequential stages of the replication cycle of a virus inside a susceptible host cell.

Step 2: Detailed Explanation:
Let us analyze the chronological order of the stages of viral replication:
-

Step 1: Entry Phase (C):
Before replication can begin, the virus must enter the host cell.
This phase includes attachment (adsorption of viral surface proteins to host cell receptors), penetration (entry of the virus into the cytoplasm), and uncoating (release of the viral nucleic acid from its protein capsid).
This corresponds to step (C).
- Early Transcription/Translation (D):
Once the viral genome is free in the host cytoplasm or nucleus, transcription of viral genes begins.
This results in the synthesis of viral messenger RNA (mRNA), which is then translated by host ribosomes into early functional (non-structural) proteins.
These early proteins include enzymes (like polymerases) required for viral genome replication.
This corresponds to step (D).
-

Step 2: Late Translation (A):
Following genomic replication, late transcription and translation occur to synthesize the viral structural proteins (such as capsid and envelope proteins) that will form the physical structure of the progeny virions.
This corresponds to step (A).
-

Step 3: Exit Phase (B):
In this final stage, the newly synthesized viral genomes and structural proteins are packaged together during assembly.
The progeny virions undergo maturation to become infectious, and they are subsequently released from the host cell via lysis, budding, or exocytosis.
This corresponds to step (B).
Therefore, the correct chronological order is:
\[ \text{Entry (C)} \rightarrow \text{Functional Protein Synthesis (D)} \rightarrow \text{Structural Protein Synthesis (A)} \rightarrow \text{Release (B)} \] This matches the sequence (C), (D), (A), (B), which corresponds to Option (A).

Step 3: Final Answer:
The correct sequential order of the steps is (C), (D), (A), (B).
Therefore, the correct choice is Option (A).