Section 3: Genetics, Cellular and Molecular Biology
DNA replication, transcription, translation
Subtopic: Fundamentals of DNA replication, transcription, translation
Question Statement:
g cm
. If the biomass reach their terminal velocity instantaneously, the
biomass settling time in min (rounded off to two decimal places) is _
Options:
(A) double-stranded DNA
(B) double-stranded RNA
(C) negative-sense single-stranded RNA
(D) | positive-sense single-stranded RNA
Official Answer Key:
D
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2021 Q.11)**
**1. Governing Concept**:
- **Topic**: Virology & Coronavirus Genome Structure
- Coronaviruses (family *Coronaviridae*, e.g., SARS-CoV, MERS-CoV, SARS-CoV-2) possess a **positive-sense single-stranded RNA (+ssRNA)** genome.
- It is among the largest known RNA viral genomes ($\sim 27-32\text{ kb}$), capped at the 5' end and polyadenylated at the 3' end, allowing it to be translated directly by host ribosomes upon cellular entry.
**2. Option Analysis**:
- **Option (A) [double-stranded DNA] is INCORRECT**: Characteristic of adenoviruses, herpesviruses, poxviruses.
- **Option (B) [double-stranded RNA] is INCORRECT**: Characteristic of reoviruses and rotaviruses.
- **Option (C) [negative-sense single-stranded RNA] is INCORRECT**: Characteristic of influenza, rabies, and rhabdoviruses.
- **Option (D) [positive-sense single-stranded RNA] is CORRECT**: Defining viral genome architecture of coronaviruses.
**3. Final Answer**:
- **Correct Choice**: **D**
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.