Q.66 Monkey pox is caused by a
(A) double–stranded DNA virus
(B) single–stranded DNA virus
(C) double–stranded RNA virus
(D) single–stranded RNA virus
Monkeypox is caused by a double-stranded DNA virus from the Orthopoxvirus genus in the Poxviridae family.
Correct Answer
(A) double-stranded DNA virus
Option Analysis
Monkeypox virus (MPXV) belongs to the Orthopoxvirus genus, which contains large, brick-shaped viruses with linear double-stranded DNA genomes of about 190-200 kb encoding around 190 proteins. This distinguishes it from RNA viruses and single-stranded DNA viruses.
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(A) Double-stranded DNA virus: Correct, as MPXV is a dsDNA virus that replicates in the host cell cytoplasm using its own enzymes, similar to smallpox virus (variola).
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(B) Single-stranded DNA virus: Incorrect; ssDNA viruses (e.g., parvoviruses) are small, non-enveloped, and lack the large genome and envelope of poxviruses.
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(C) Double-stranded RNA virus: Incorrect; dsRNA viruses (e.g., reoviruses) replicate in the cytoplasm but have segmented RNA genomes and cause different diseases like rotavirus gastroenteritis.
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(D) Single-stranded RNA virus: Incorrect; ssRNA viruses (e.g., coronaviruses, influenza) include positive-sense (e.g., picornaviruses) or negative-sense types and mutate rapidly, unlike stable dsDNA poxviruses.
Monkeypox double-stranded DNA virus, now termed mpox virus (MPXV), drives outbreaks with its stable 197 kb linear dsDNA genome in the Poxviridae family. This Orthopoxvirus relative to smallpox replicates cytoplasmically, producing enveloped brick-shaped virions (200-250 nm).
Virus Structure
MPXV features a lipoprotein envelope, lateral bodies, and a core with dsDNA hairpin ends plus inverted terminal repeats for replication. Genes in the central genome handle transcription/assembly, while ends code host-interaction factors like virulence proteins.
Clades and Transmission
Two clades exist: Clade I (Ia/Ib, more severe) and Clade II (IIa/IIb, 2022 outbreak strain), sharing 170 orthologs but differing in virulence genes. Zoonotic spread occurs via rodents/monkeys to humans through lesions, fluids, or fomites; human-to-human via contact.
Comparison to Other Viruses
| Virus Type | Genome | Family/Examples | Key Difference from MPXV |
|---|---|---|---|
| dsDNA (Correct) | Linear dsDNA (~200 kb) | Poxviridae (smallpox, vaccinia) | Matches MPXV stability, cytoplasmic replication |
| ssDNA | ssDNA (4-6 kb) | Parvoviridae (parvovirus B19) | Tiny, nuclear replication, no envelope |
| dsRNA | Segmented dsRNA | Reoviridae (rotavirus) | Segmented, no envelope, gastroenteritis |
| ssRNA | ssRNA (+/- sense) | Coronaviridae, Orthomyxoviridae | High mutation rate, nuclear/cytoplasmic variance |
This stability aids smallpox vaccine cross-protection against mpox. For CSIR NET aspirants, note dsDNA classification excludes RNA options.
