Q.25 Severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) is caused by a
- Single-stranded RNA virus
- Double-stranded RNA virus
- Single-stranded DNA virus
- Double-stranded DNA virus
SARS-CoV-2, the virus responsible for COVID-19, is a single-stranded RNA virus. This makes option A the correct answer in the multiple-choice question.
Option Analysis
Single-stranded RNA virus: Correct. SARS-CoV-2 belongs to the Coronaviridae family and has a positive-sense, single-stranded RNA (+ssRNA) genome approximately 30 kb long. This genome directly acts as mRNA for translation upon entering host cells, enabling rapid replication.
Double-stranded RNA virus: Incorrect. Double-stranded RNA (dsRNA) viruses, like rotaviruses, have segmented genomes and use RNA-dependent RNA polymerase differently; coronaviruses do not fit this structure.
Single-stranded DNA virus: Incorrect. These include parvoviruses (e.g., Parvovirus B19); SARS-CoV-2 uses RNA, not DNA, as its genetic material.
Double-stranded DNA virus: Incorrect. Examples include herpesviruses or adenoviruses; DNA viruses require transcription to RNA first, unlike the direct translation of SARS-CoV-2’s RNA genome.
SARS-CoV-2 single-stranded RNA virus is the key pathogen behind the global COVID-19 pandemic. This positive-sense single-stranded RNA virus features a ~30 kb genome that enables efficient host cell infection.
Genome Features
The SARS-CoV-2 single-stranded RNA virus genome encodes structural proteins (spike, envelope, membrane, nucleocapsid) and non-structural proteins for replication. Its +ssRNA nature allows direct translation without host DNA involvement.
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High uracil content (32%) with cytosine/guanine bias.
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Open reading frames (ORF1a/b) produce polyproteins cleaved into 16 nsps.
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Envelope with spike protein targets ACE2 receptors.
Why Single-Stranded RNA?
Unlike double-stranded RNA viruses (e.g., reoviruses), SARS-CoV-2 single-stranded RNA virus replicates via RNA-dependent RNA polymerase, forming negative-sense intermediates. DNA viruses (ss/ds) are ruled out as they lack this RNA blueprint.
Virus Type Example Genome SARS-CoV-2 Match? ssRNA (+) SARS-CoV-2 Single-stranded RNA Yes dsRNA Rotavirus Double-stranded RNA No ssDNA Parvovirus Single-stranded DNA No dsDNA Adenovirus Double-stranded DNA No Exam Relevance
For life sciences exams, note SARS-CoV-2 single-stranded RNA virus classification under Betacoronavirus. Its mutation rate drives variants like Omicron.
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