Section 3: Genetics, Cellular and Molecular Biology
Recombinant DNA technology
Subtopic: Fundamentals of Recombinant DNA technology
Question Statement:
Emerging viruses such as SARS-CoV2 cause epidemics. Which of the following
process(es) contribute to the rise of such viruses?
Options:
(A) Agrobacterium
(B) CaCl2 mediated plasmid uptake
(C) Electroporation
(D) Gene gun
Official Answer Key:
A;B;C
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2022 Q.52)**
**1. Governing Concept**:
- **Topic**: Virology & Viral Evolution and Epidemic Emergence
- The emergence and rapid spread of pandemic viruses (such as SARS-CoV-2 and Influenza A) are driven by evolutionary mechanisms:
1. **Antigenic Drift**: Accumulation of point mutations during replication due to error-prone viral polymerases (e.g. RNA-dependent RNA polymerase lacking proofreading).
2. **Recombination / Reassortment (Antigenic Shift)**: Template switching in coronaviruses during co-infection, or segment swapping in segmented genomes like influenza, producing novel chimeric strains with altered tropism.
3. **Zoonotic Spillover**: Adaptation of viral surface spike/hemagglutinin glycoproteins to human cellular receptors (e.g. ACE2) overcoming species barriers.
**2. Option Analysis**:
- **Option (A) [Accumulation of mutations in the viral genome] is CORRECT**: Generates antigenic variants that evade host immune surveillance.
- **Option (B) [Zoonotic transmission from animal reservoirs to humans] is CORRECT**: The principal origin of SARS, MERS, and SARS-CoV-2 outbreaks.
- **Option (C) [Genetic recombination among viral strains] is CORRECT**: Frequent coronavirus mechanism driving structural gene diversification.
- **Option (D) is INCORRECT**: Bacterial conjugation is a prokaryotic DNA transfer mechanism not present in viral life cycles.
**3. Final Answer**:
- **Correct Options**: **A, B, C**
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