Question

3'-Azido-2',3'-dideoxy thymidine (AZT) with the structure shown above has potential to work as a drug against HIV because:
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• A. of its ability to competitively bind reverse transcriptase and inhibit its activity
• B. its addition at the 3' end of the growing DNA strand will terminate viral DNA synthesis
• C. it stacks between successive nucleotide bases thereby inhibiting viral DNA synthesis
• D. it binds to the minor groove of the viral DNA thereby inhibiting the binding of reverse transcriptase

Hint:

AZT works by terminating DNA synthesis at the 3' end, preventing further nucleotide additions during viral replication.

Answer 1

The Correct Option is B

Step 1: Understanding AZT's mechanism of action.
AZT (3'-Azido-2',3'-dideoxy thymidine) is a nucleoside analog that inhibits the reverse transcriptase enzyme by acting as a chain terminator. When incorporated into the growing viral DNA strand, the 3'-azido group prevents the addition of the next nucleotide, effectively halting DNA synthesis.

Step 2: Analyzing the options.
- (A) of its ability to competitively bind reverse transcriptase and inhibit its activity: Incorrect. AZT works as a chain terminator, not by competitive inhibition.
- (B) its addition at the 3' end of the growing DNA strand will terminate viral DNA synthesis: Correct — AZT's structure prevents the addition of further nucleotides, thereby terminating viral DNA synthesis.
- (C) it stacks between successive nucleotide bases thereby inhibiting viral DNA synthesis: Incorrect. AZT's mechanism is chain termination, not base stacking.
- (D) it binds to the minor groove of the viral DNA thereby inhibiting the binding of reverse transcriptase: Incorrect. AZT does not function by binding to the minor groove of the viral DNA.

Step 3: Conclusion.
The correct answer is (B) because AZT terminates the growing DNA strand at the 3' end, stopping viral DNA synthesis.