Question

Arrange the following steps of retrovirus replication sequentially:
• [(A)] Production of viral DNA by reverse transcriptase
• [(B)] Introduction of viral RNA into host cell
• [(C)] Production of new viral RNA by host cell
• [(D)] Incorporation of viral DNA into host genome Choose the correct answer from the options given below:

• A. B \(\rightarrow\) A \(\rightarrow\) D \(\rightarrow\) C
• B. A \(\rightarrow\) B \(\rightarrow\) D \(\rightarrow\) C
• C. B \(\rightarrow\) D \(\rightarrow\) A \(\rightarrow\) C
• D. A \(\rightarrow\) D \(\rightarrow\) B \(\rightarrow\) C

Hint:

Retrovirus replication follows the sequence: \[ \text{RNA} \rightarrow \text{DNA} \rightarrow \text{Integration} \rightarrow \text{New Viral RNA} \] A simple mnemonic is: \[ \boxed{\text{Enter} \rightarrow \text{Reverse Transcribe} \rightarrow \text{Integrate} \rightarrow \text{Replicate}} \] This is the characteristic feature of HIV and other retroviruses.

Answer 1

The Correct Option is A

Step 1: Entry of viral RNA into the host cell. A retrovirus first enters the host cell and releases its genetic material. Thus the first step is: \[ (B)\ \text{Introduction of viral RNA into host cell} \]

Step 2: Formation of viral DNA. Retroviruses possess the enzyme reverse transcriptase which synthesizes DNA from RNA. Therefore: \[ (A)\ \text{Production of viral DNA by reverse transcriptase} \] occurs next.

Step 3: Integration into host genome. The newly formed viral DNA becomes integrated into the host chromosome. Thus: \[ (D)\ \text{Incorporation of viral DNA into host genome} \] is the third step.

Step 4: Synthesis of new viral RNA. The integrated viral DNA utilizes the host cellular machinery to produce new viral RNA. Therefore: \[ (C)\ \text{Production of new viral RNA by host cell} \] is the final step. Hence the correct sequence is: \[ \boxed{B \rightarrow A \rightarrow D \rightarrow C} \] Therefore, the correct answer is: \[ \boxed{\text{(A)}} \]