Lesson eLearning

Which point mutation in the rpoB gene of Mycobacterium tuberculosis confers resistance to rifampicin?

easy MCQ 1 mark Class 12 · Biology · Evolution
  1. T→C transition at codon 450
  2. G→A at codon 600
  3. C→T at codon 150
  4. A→G at codon 300
Answer
T→C transition at codon 450

The correct answer is T→C transition at codon 450 — Step 4: Therefore the correct mutation is the T→C transition at codon 450.

Step-by-step solution

  1. Step 1: Identify the rpoB gene, which encodes the β‑subunit of RNA polymerase, the target of rifampicin.
  2. Step 2: Recall that rifampicin binds to rpoB near codon 450; mutations here reduce binding affinity.
  3. Step 3: Among common mutations, a T→C transition at codon 450 is well‑documented to confer resistance.
  4. Step 4: Therefore the correct mutation is the T→C transition at codon 450.
Common mistake: Confusing the codon position; many students pick codon 600 or 300 instead of 450.

Concept tested: Antibiotic resistance via point mutation

Published · How this solution was prepared and checked

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