Subtopic: Fundamentals of Cell structure and signaling
Question Statement:
Koch's postulate was established by Robert Koch while working on a disease
caused by
Options:
(A) Mycobacterium tuberculosis
(B) Bacillus anthracis
(C) Streptococcus pneumoniae
(D) Bacillus subtilis
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2025 Q.11)**
**1. Governing Concept**:
- **Topic**: Immunology & Monoclonal Antibody Diversity
- Monoclonal antibodies (mAbs) derived from a single clone of hybridoma cells:
- All antibodies produced by a single clone share **identical epitope specificity**, **identical idiotype**, and **identical affinity constant ($K_a$)**.
- In contrast, polyclonal antisera recognize multiple distinct epitopes on an antigen with varying affinities.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: Monoclonals are monospecific, not polyspecific.
- **Option (B) is CORRECT**: Accurately recognizes that mAbs bind to a single, unique epitope with uniform binding affinity.
- **Option (C) is INCORRECT**: They do not cross-react indiscriminately with diverse antigens.
- **Option (D) is INCORRECT**: Heavy and light chain sequences within a single clone are homogeneous.
**3. Final Answer**:
- **Correct Choice**: **B**
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