Section 4: Bioprocess Engineering and Process Biotechnology
Bioreactor types, scale-up
Subtopic: Fundamentals of Bioreactor types, scale-up
Question Statement:
For a specific bioreactor configuration, the power requirement for a
Rushton-turbine impeller agitating an unaerated Newtonian fluid in
the turbulent regime will be
Options:
(A) proportional to the stirring speed of the impeller
(B) proportional to the square of the stirring speed of the impeller
(C) proportional to the cube of the stirring speed of the impeller
(D) inversely proportional of the stirring speed of the impeller
Official Answer Key:
C
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2025 Q.44)**
**1. Governing Concept**:
- **Topic**: Molecular Genetics & Transposable Genetic Elements
- Bacterial transposons are categorized based on their structural organization:
- **Insertion Sequences (IS elements)**: Simplest mobile elements (~750–2000 bp); encode only the **transposase** enzyme required for mobility, flanked by terminal **inverted repeats (IRs)**.
- **Composite (Compound) Transposons** (e.g. Tn9, Tn10, Tn5): Contain a central region carrying accessory genes (e.g., antibiotic resistance) flanked by two matching IS elements in direct or inverted orientation.
- **Non-composite Transposons** (e.g. Tn3): Lack flanking IS elements; encode transposase, resolvase, and accessory genes between terminal inverted repeats.
**2. Option Analysis**:
- **Option (A) is CORRECT**: Insertion sequences (IS elements) are the minimal autonomous transposable elements encoding only their own transposase bounded by terminal inverted repeats.
- **Option (B) is INCORRECT**: Composite transposons carry accessory passenger genes (such as antibiotic resistance).
- **Option (C) is INCORRECT**: Integrons are gene-capture platforms, not autonomous insertion elements.
- **Option (D) is INCORRECT**: Plasmids are autonomously replicating extrachromosomal replicons, not simple transposable elements.
**3. Final Answer**:
- **Correct Choice**: **A**
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