GATE 2021 BT – Question 46

General Biology · Microbiology: Microbial diseases, host-pathogen interactions, antibiotics and resistance, two-component system, bacterial communication, viruses · 2 marks · Multiple select

Which antimicrobial agents are growth-factor analogs?

5-Fluorouracil
Isoniazid
Sulfanilamide
Tetracycline

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Correct answer: (A) 5-Fluorouracil; (B) Isoniazid; (C) Sulfanilamide

Explanation

A **growth-factor analogue** (antimetabolite) is a molecule that resembles an essential growth factor or metabolite so closely that it competes with it and blocks a pathway.

**5-Fluorouracil:** an analogue of the pyrimidine uracil/thymine, it blocks thymidylate synthase. ✓
**Isoniazid:** structurally similar to nicotinamide (a vitamin); it interferes with mycolic acid synthesis in mycobacteria and is classically grouped with growth-factor analogues. ✓
**Sulfanilamide:** an analogue of **p-aminobenzoic acid (PABA)**, it blocks folic acid synthesis. ✓
**Tetracycline:** binds the 30S ribosomal subunit and inhibits translation. It is not a structural analogue of a growth factor. ✗

Answer **A, B and C**.

Official GATE 2021 answer key: https://gate2026.iitg.ac.in/doc/download/Answer_keys2021/bt_2021.pdf