Correctly match the following Product classes with their representative
Products.
Product class Product
P. Biofuel 1. Cellulase
Q. Bioplastic 2. Cephalosporin
R. Industrial enzyme 3. Butanol
S. Antibiotic 4. Poly-lactic acid
5. Rituximab
Options:
(A) P-1; Q-5; R-3; S-2
(B) P-3; Q-4; R-5; S-2
(C) P-3; Q-2; R-1; S-5
(D) P-3; Q-4; R-1; S-2
Official Answer Key:
D
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2025 Q.19)**
**1. Governing Concept**:
- **Topic**: Bioinformatics & Pairwise Sequence Alignment Scoring Matrices
- Amino acid substitution matrices (PAM and BLOSUM):
- **BLOSUM matrices (BLOcks SUbstitution Matrix)**: Derived from local alignments of conserved protein blocks without gaps (Henikoff & Henikoff).
- Higher numbered BLOSUM matrices (e.g. **BLOSUM80**) are based on alignments of blocks with $\ge 80\%$ identity and are optimal for aligning **closely related sequences**.
- Lower numbered BLOSUM matrices (e.g. **BLOSUM45**) are derived from sequences with $\ge 45\%$ identity and are designed for finding **distantly related sequences**.
- **BLOSUM62** is the standard default for general searches.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: Higher PAM numbers (e.g. PAM250) are for distantly related sequences, whereas lower numbers (PAM1) are for close homologs.
- **Option (B) is CORRECT**: BLOSUM62 is calibrated for intermediate evolutionary distances, while lower numbers (BLOSUM45) detect distant relationships and higher numbers (BLOSUM80) detect close homologs.
- **Option (C) is INCORRECT**: PAM matrices are derived from global alignments of closely related families, not ungapped blocks.
- **Option (D) is INCORRECT**: Inverts the BLOSUM matrix numbering scale.
**3. Final Answer**:
- **Correct Choice**: **B**
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