Subtopic: Fundamentals of Biomolecules, enzyme kinetics
Question Statement:
Which one of the following is NOT used for the measurement of cell viability in animal cell
culture?
(A) Trypan blue dye exclusion (B) Tetrazolium (MTT) assay
(C) LDH activity in the culture medium (D) Coulter counter
Options:
(A) Trypan blue dye exclusion
(B) Tetrazolium (MTT) assay
(C) LDH activity in the culture medium
(D) Coulter counter
Official Answer Key:
D
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2016 Q.12)**
**1. Governing Concept & Question Classification**:
- **Section**: BT
- **Question Type**: **MCQ** (1 Mark)
- **Topic**: Microbiology & Virology (Viral Baltimore Classification & Genome Types)
**2. Detailed Step-by-Step Analysis**:
- Let us review the viral genome structure across the families:
1. **Poxviridae** (Group I): Large enveloped viruses with **double-stranded DNA (dsDNA)** genomes (e.g., Variola virus, Vaccinia virus).
2. **Herpesviridae** (Group I): Enveloped viruses with linear **dsDNA** genomes (e.g., Herpes simplex virus, Epstein-Barr virus).
3. **Adenoviridae** (Group I): Non-enveloped icosahedral viruses with linear **dsDNA** genomes.
4. **Parvoviridae** (Group II): Small (18–26 nm), non-enveloped icosahedral viruses containing a linear **single-stranded DNA (ssDNA)** genome of approximately 5 kb (e.g., Parvovirus B19, adeno-associated virus AAV).
- Therefore, **Parvoviridae** is the family possessing single-stranded DNA.
- **Option-by-Option Evaluation**:
- **Option (A) [INCORRECT]**: Poxviridae genomes are double-stranded DNA.
- **Option (B) [INCORRECT]**: Herpesviridae genomes are double-stranded DNA.
- **Option (C) [INCORRECT]**: Adenoviridae genomes are double-stranded DNA.
- **Option (D) [CORRECT]**: Parvoviridae genomes are single-stranded DNA (ssDNA).
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **D**
- **Scoring Criteria**: +1.0 Mark (Negative marking: -0.33 marks).
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