41. Match the drugs in Group I with their mechanism of action in Group II.
| Group I | Group II |
|---|---|
| P) Paclitaxel | 1) Inhibits protein translation |
| Q) Colchicine | 2) Inhibits microtubule depolymerization |
| R) Etoposide | 3) Inhibits DNA replication |
| S) Methotrexate | 4) Alkylates DNA |
| 5) Inhibits dihydrofolate reductase | |
| 6) Inhibits microtubule polymerization |
(A) P-1, Q-6, R-3, S-4
(B) P-2, Q-6, R-3, S-5
(C) P-1, Q-3, R-6, S-5
(D) P-2, Q-3, R-6, S-4
Step-by-Step Matching (Conceptual Explanation)
P) Paclitaxel → Inhibits microtubule depolymerization (2)
Paclitaxel stabilizes microtubules and prevents their depolymerization, leading to mitotic arrest in cancer cells.
Correct match: P–2
Q) Colchicine → Inhibits microtubule polymerization (6)
Colchicine binds to tubulin and prevents microtubule formation, inhibiting mitosis (metaphase arrest).
Correct match: Q–6
R) Etoposide → Inhibits DNA replication (3)
Etoposide inhibits topoisomerase II, preventing DNA strand re-ligation, which blocks DNA replication and transcription.
Correct match: R–3
S) Methotrexate → Inhibits dihydrofolate reductase (5)
Methotrexate is a folic acid antagonist that inhibits DHFR, reducing thymidine synthesis and DNA replication.
Correct match: S–5
Final Correct Answer
Option (B)
P–2, Q–6, R–3, S–5
Introduction
Understanding how to match the drugs with their mechanism of action is a high-yield topic in pharmacology and frequently asked in competitive exams like NEET, GPAT, and university assessments. This article explains a classic MCQ involving anticancer and antimitotic drugs, breaking down each option with clear mechanisms to help you choose the correct answer confidently.
Mechanism of Action Explained
Paclitaxel
Paclitaxel works by stabilizing microtubules and preventing their breakdown. Since normal cell division requires microtubule depolymerization, this action causes mitotic arrest and apoptosis in cancer cells.
➡ Mechanism: Inhibits microtubule depolymerization
Colchicine
Colchicine binds to tubulin, blocking the formation of microtubules. This prevents chromosome separation during cell division.
➡ Mechanism: Inhibits microtubule polymerization
Etoposide
Etoposide interferes with DNA replication by inhibiting topoisomerase II, an enzyme essential for relieving DNA supercoiling during replication.
➡ Mechanism: Inhibits DNA replication
Methotrexate
Methotrexate is a folic acid antagonist that blocks dihydrofolate reductase, leading to decreased synthesis of thymidine and purines required for DNA synthesis.
➡ Mechanism: Inhibits dihydrofolate reductase
Correct Drug–Mechanism Match
| Drug | Mechanism |
|---|---|
| Paclitaxel | Inhibits microtubule depolymerization |
| Colchicine | Inhibits microtubule polymerization |
| Etoposide | Inhibits DNA replication |
| Methotrexate | Inhibits dihydrofolate reductase |
Final Answer
Option (B): P–2, Q–6, R–3, S–5
Exam Tip
Paclitaxel stabilizes microtubules, Colchicine prevents their formation, Etoposide blocks topoisomerase II, and Methotrexate blocks folate metabolism.
Remembering these core actions helps solve multiple MCQs quickly.
