Section 3: Genetics, Cellular and Molecular Biology
Classical Genetics and Epistasis
Subtopic: Mendelian Genetics & Gene Interactions
Question Statement:
Match the carbohydrates in Column I with the correct glycosidic linkages involved
in Column II.
Column I Column II
P. Amylose 1. β (1 4)
Q. Sucrose 2. α (1 4)
R. Amylopectin 3. α1 β2
S. Cellulose 4. α (1 4), α (1 6)
Options:
(A) P-4; Q-3; R-2; S-1
(B) P-2; Q-1; R-4; S-3
(C) P-2; Q-3; R-4; S-1
(D) P-1; Q-3; R-4; S-2
Official Answer Key:
C
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2026 Q.23)**
**1. Governing Concept**:
- **Topic**: Biochemistry & Glycosidic Linkages in Disaccharides
- Standard disaccharide glycosidic bond architectures:
1. **Maltose**: Two $\alpha$-$D$-glucopyranose units linked by an **$\alpha(1 \to 4)$** glycosidic bond.
2. **Lactose**: $\beta$-$D$-galactopyranose linked to $\beta$-$D$-glucopyranose via a **$\beta(1 \to 4)$** glycosidic bond.
3. **Sucrose**: $\alpha$-$D$-glucopyranose linked to $\beta$-$D$-fructofuranose via an **$\alpha(1 \leftrightarrow 2)\beta$** non-reducing head-to-head glycosidic linkage.
4. **Trehalose**: Two $\alpha$-$D$-glucose units linked via an **$\alpha(1 \leftrightarrow 1)\alpha$** non-reducing bond.
**2. Option Analysis**:
- Matching Column I carbohydrates with Column II glycosidic bonds:
- Maltose $\rightarrow \alpha(1 \to 4)$
- Lactose $\rightarrow \beta(1 \to 4)$
- Sucrose $\rightarrow \alpha(1 \leftrightarrow 2)\beta$
- **Option (C) is CORRECT**: Perfectly aligns every sugar with its canonical linkage.
- **Options (A), (B), and (D) are INCORRECT**: Misassign anomeric configurations ($\alpha$ vs $\beta$) or carbon numbers.
**3. Final Answer**:
- **Correct Choice**: **C**
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