Subtopic: Fundamentals of Downstream processing (chromatography, filtration)
Question Statement:
A DNA sequence, 5'-ATGGACGTGCTTCCCAAAGCATCGGGC-3', is mutated to obtain
P. 5'-ATGGACGTGCTTCaCAAAGCATCGGGC-3'
Q. 5'-ATGGACGTGCTTCCCgAAAGCATCGGGC-3'
R. 5'-ATGGACGTGCTTCC-AAAGCATCGGGC-3'
S. 5'-ATGGACGTGCTTCCCAAtGCATCGGGC-3'
T. 5'-ATGGACGaGCTTCCCAAAGCATCGGGC-3'
[Point mutations are shown in the lower case or '-' within the sequences]
Which of the above mutant sequences DO NOT have frame-shift?
(A) P, Q and S (B) P, S and T (C) Q, R and S (D) Q, S and T
Options:
(A) P, Q and S
(B) P, S and T
(C) Q, R and S
(D) Q, S and T
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2016 Q.28)**
**1. Governing Concept & Question Classification**:
- **Section**: BT
- **Question Type**: **MCQ** (1 Mark)
- **Topic**: Environmental Biotechnology (Wastewater Treatment Stages)
**2. Detailed Step-by-Step Analysis**:
- Wastewater and industrial effluent treatment consists of sequentially distinct stages:
1. **Primary treatment**: Physical processes (screening, grit removal, sedimentation/clarification) to remove large settleable solids and floating debris.
2. **Secondary treatment**: A **biological treatment** process where aerobic or anaerobic microbial consortia (e.g., activated sludge, trickling filters, sequencing batch reactors, oxidation ponds, or anaerobic digesters) metabolize dissolved organic matter, substantially reducing the Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD).
3. **Tertiary treatment**: Advanced physicochemical and disinfection processes (sand filtration, activated carbon adsorption, reverse osmosis, chlorination, UV ozonation) to remove recalcitrant pollutants, heavy metals, and nutrients (N and P).
4. **Quaternary treatment**: Targeted destruction of micropollutants (pharmaceuticals, endocrine disruptors).
- Therefore, a biological process is fundamentally involved in the **secondary** treatment.
- **Option-by-Option Evaluation**:
- **Option (A) [INCORRECT]**: Primary treatment relies on physical gravity separation.
- **Option (B) [CORRECT]**: Secondary treatment is the dedicated biological treatment stage utilizing microorganisms to degrade dissolved organic matter.
- **Option (C) [INCORRECT]**: Tertiary treatment uses advanced physicochemical/disinfection methods.
- **Option (D) [INCORRECT]**: Quaternary treatment targets emerging micropollutants.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **B**
- **Scoring Criteria**: +1.0 Mark (Negative marking: -0.33 marks).
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