DNA viruses vs RNA viruses
How to tell DNA viruses and RNA viruses apart when a board question makes them look alike.
DNA viruses mostly replicate in nucleus; RNA viruses mostly replicate in cytoplasm, with poxvirus, influenza, and retrovirus as key exceptions.
Side by side
DNA viruses generally replicate in the nucleus and include herpesviruses, adenovirus, papillomavirus, polyomavirus, parvovirus, poxvirus, and hepadnavirus.
RNA viruses generally replicate in the cytoplasm and include picorna, calici, toga, flavi, corona, rhabdo, filo, paramyxo, orthomyxo, bunya, arena, and retroviruses.
Most DNA viruses use host or viral DNA polymerases in the nucleus, with poxvirus as the major cytoplasmic DNA-virus exception.
RNA viruses require RNA-dependent RNA polymerase or reverse transcriptase logic, with influenza and retroviruses involving nuclear steps.
Nuclear replication clues, DNA genome, oncogenic DNA virus associations, and exceptions such as pox cytoplasmic replication support DNA virus grouping.
Cytoplasmic replication clues, segmented RNA, negative-sense RNA polymerase needs, or retroviral reverse transcription support RNA virus grouping.
The trap
Genome rules are broad shortcuts, so high-yield exceptions must be attached to the rule.
The repair move
For viral genome grouping, state the default replication site and then check for classic exceptions.
Try a free question
CoreA pathology slide shows characteristic Cowdry type A intranuclear inclusion bodies in epithelial cells from a vesicular skin lesion. The virus belongs to a family that replicates its genome in the host nucleus. Which class of virus is most consistent with this finding?
Show answer and explanation
Answer: A. Double-stranded DNA virus replicating in the nucleus. Herpesviruses are double-stranded DNA viruses that replicate in the nucleus, producing characteristic Cowdry type A intranuclear inclusions.
Why the other choices are tempting
- B. Most positive-sense RNA viruses replicate in the cytoplasm and would not produce nuclear inclusions.
- C. Segmented dsRNA viruses (Reoviridae such as rotavirus) replicate in cytoplasm without nuclear inclusion formation.
- D. Negative-sense RNA viruses generally replicate in cytoplasm and produce cytoplasmic Negri bodies (rabies) rather than nuclear Cowdry bodies.
- E. Hepatitis D is a defective virus requiring HBV; this does not describe herpesvirus biology.
Flashcards
Tap a card to flip it.
Where do most DNA viruses replicate?
Most DNA viruses replicate in the nucleus.
What DNA virus exception replicates in cytoplasm?
Poxvirus is the classic DNA virus that replicates in the cytoplasm.
Quick answers
What is the fastest way to tell DNA viruses from RNA viruses?
DNA viruses mostly replicate in nucleus; RNA viruses mostly replicate in cytoplasm, with poxvirus, influenza, and retrovirus as key exceptions.
What is the key clue for DNA viruses?
DNA viruses generally replicate in the nucleus and include herpesviruses, adenovirus, papillomavirus, polyomavirus, parvovirus, poxvirus, and hepadnavirus.
What is the key clue for RNA viruses?
RNA viruses generally replicate in the cytoplasm and include picorna, calici, toga, flavi, corona, rhabdo, filo, paramyxo, orthomyxo, bunya, arena, and retroviruses.
What is the common trap with DNA viruses vs RNA viruses?
Genome rules are broad shortcuts, so high-yield exceptions must be attached to the rule.