Virology 1 Flashcards
What is a virus?
A virus is an obligate intracellular parasite that requires a host cell to replicate.
What are the four main shapes of viruses?
Head + tail, Helical, Icosahedral, and Pleomorphic (variable).
How are viruses classified?
Baltimore classification (based on genome type) and the International Committee on Taxonomy of Viruses (ICTV) system (based on biological taxonomy).
What are the main stages of viral replication?
- Attachment
- Entry
- Uncoating
- Replication
- Assembly
- Release
What is a nucleocapsid?
A nucleocapsid is the combination of viral genetic material (RNA or DNA) and its protective protein coat.
Polio virus is an
icosahedral virus, ~22nm in diameter.
Influenza virus has a pleomorphic shape and contains
haemagglutinin and neuraminidase glycoproteins.
Baltimore classification groups viruses into seven categories based on
genome type.
Viral RNA polymerase is essential for
replication in RNA viruses.
Poliomyelitis is a vaccine-preventable disease that can cause
paralysis in ~1% of infections.
Viruses can replicate independently outside a host cell.
False
Poliovirus uses the CD155 receptor to enter host cells.
True
All viruses are enveloped.
False – some are non-enveloped
RNA viruses replicate using host DNA polymerase.
False – they use RNA-dependent RNA polymerase.
The smallest known virus by diameter is ______________.
Picornaviridae, e.g., Polio virus
The structural proteins of the Polio virus capsid include ______________.
VP1, VP2, VP3, VP4
The enzyme ______________ is required for reverse transcription in retroviruses.
Reverse transcriptase
In the Baltimore classification system, Group IV viruses have ______________ genomes.
Positive-sense single-stranded RNA
Which of the following viruses has an icosahedral capsid?
a) Influenza virus
b) Poliovirus
c) Tobacco Mosaic Virus
d) Herpes simplex virus
Answer: (b) Poliovirus
Which classification system is based on the genome type of viruses?
a) ICTV System
b) Baltimore Classification
c) Linnaean System
d) Koch’s Postulates
Answer: (b) Baltimore Classification
What is the primary receptor for poliovirus entry into host cells?
a) CD4
b) ACE2
c) CD155
d) Integrin
Answer: (c) CD155
A patient presents with flu-like symptoms and later develops muscle weakness and paralysis. What virus is the likely cause, and what laboratory tests can confirm the diagnosis?
Likely cause: Poliovirus; Confirmatory tests: PCR analysis of fecal samples, sequencing of viral RNA.
A new RNA virus is discovered that replicates using an RNA-dependent RNA polymerase. Which Baltimore classification group does it belong to?
It belongs to Group V (negative-sense ssRNA viruses).
A virologist is studying a novel virus that integrates its genome into the host DNA. What enzyme is required for this process, and which viral family does it most likely belong to?
Enzyme: Reverse transcriptase; Viral family: Retroviridae.
Capsid:
Protein coat surrounding the viral genome.
Envelope:
Lipid membrane derived from the host cell, present in some viruses.
Virion:
A complete, infectious virus particle.
Reverse Transcriptase:
Enzyme that synthesizes DNA from an RNA template.
Haemagglutinin & Neuraminidase:
Glycoproteins found in Influenza virus that facilitate attachment and release.
