Section 4: Bioprocess Engineering and Process Biotechnology
Mass transfer in bioprocesses (kLa)
Subtopic: Fundamentals of Mass transfer in bioprocesses (kLa)
Question Statement:
Match the genetic disorders in Column I to the corresponding underlying cause in
Column II
Column I Column II
P. Klinefelter Syndrome 1. X-chromosome insufficiency
Q. Turner syndrome 2. DNA helicase mutations
R. Bloom syndrome 3. Nucleotide excision repair defects
S. Xeroderma pigmentosum 4. Extra X chromosome(s) in a male
Options:
(A) P-1; Q-3; R-4; S-2
(B) P-4; Q-1; R-2; S-3
(C) P-4; Q-2; R-3; S-1
(D) P-3; Q-2; R-4; S-1
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2026 Q.38)**
**1. Governing Concept**:
- **Topic**: Human Genetics & Molecular Basis of Genetic Disorders
- Pathological molecular mechanisms of human genetic diseases:
1. **Sickle Cell Anemia**: Autosomal recessive point mutation in the $\beta$-globin gene (*HBB*), specifically a transversion of $A \to T$ causing Glu6Val substitution (E6V).
2. **Huntington's Disease**: Autosomal dominant neurodegenerative disorder caused by unstable **CAG trinucleotide repeat expansion** in the huntingtin (*HTT*) gene encoding a polyglutamine tract.
3. **Cystic Fibrosis**: Autosomal recessive mutation in the *CFTR* gene, most commonly an in-frame 3 bp deletion leading to loss of phenylalanine at position 508 ($\Delta\text{F508}$).
4. **Down Syndrome**: Aneuploidy resulting from **Trisomy 21** due to maternal meiotic non-disjunction.
**2. Option Analysis**:
- Matching Column I diseases with Column II causes:
- Sickle Cell Anemia $\rightarrow$ Single base substitution in $\beta$-globin gene.
- Huntington's Disease $\rightarrow$ Trinucleotide repeat expansion (CAG).
- Down Syndrome $\rightarrow$ Aneuploidy (Trisomy 21).
- Cystic Fibrosis $\rightarrow$ Defective chloride channel (CFTR mutation).
- **Option (B) is CORRECT**: Aligns all four genetic disorders to their definitive genetic etiologies.
- **Options (A), (C), and (D) are INCORRECT**: Scramble repeat expansion with single-point substitutions.
**3. Final Answer**:
- **Correct Choice**: **B**
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