Studied by 2 people
What are viruses composed of?
A nucleic acid (DNA or RNA) and a protein coat, sometimes enclosed by an envelope.
What is a virion?
A complete, infectious viral particle with nucleic acid surrounded by a protein coat.
Define host range.
The spectrum of host cells a virus can infect.
What are capsomeres?
Protein subunits that make up the capsid of a virus.
What is the size range of viruses?
20 to 1000 nanometers.
How are helical viruses structured?
They have a cylindrical capsid with nucleic acid inside a helical structure.
Name an example of a polyhedral virus.
Poliovirus (icosahedron-shaped).
What distinguishes enveloped viruses?
They have a lipid envelope; e.g., influenza virus (enveloped helical).
What is a complex virus?
A virus with multiple layers or components, like bacteriophages and poxviruses.
What are viral spikes?
Protein projections on an envelope used for attachment to host cells.
How are viruses named in taxonomy?
Family names end in -viridae, genus names in -virus.
Provide an example of a virus family and genus.
Family: Herpesviridae; Genus: Simplexvirus (e.g., human herpesvirus 2).
Compare the lytic and lysogenic cycles of bacteriophages.
Lytic cycle ends in host cell death; lysogenic cycle integrates viral DNA into host DNA.
List the five steps of the lytic cycle.
Attachment, penetration, biosynthesis, maturation, and release.
What is the main difference in animal virus replication?
Includes uncoating of the virus after entry.
What are the four steps of the lysogenic cycle?
Attachment, entry, integration, and cell division.
What methods are used to diagnose viral infections?
Serology, microscopic identification, antigen detection, and nucleic acid detection.
How is the plaque method used?
To detect and count bacteriophages on solid media.
How does active immunity differ from passive immunity?
Active immunity is from vaccines; passive immunity involves transferred antibodies.
Name a vaccine-preventable viral disease.
Measles, Mumps, Rubella (MMR vaccine).
What is herd immunity?
Protection of the population when a high percentage is vaccinated.
What virus causes rabies?
Rabies virus, a helical virus.
Which virus uses CD4+ T lymphocytes as a host?
Human Immunodeficiency Virus (HIV)
Give an example of an enveloped polyhedral virus.
Herpes simplex virus
What are prions?
Infectious proteins causing diseases like scrapie and mad cow disease
Who proposed the prion hypothesis?
Stanley Prusiner
Compare enveloped and non-enveloped viruses.
Enveloped viruses have a lipid layer, while non-enveloped viruses lack this layer
How do DNA and RNA viruses differ?
DNA viruses replicate using host DNA machinery; RNA viruses often require reverse transcription or RNA polymerase
Name a broad-host-range virus.
Rabies virus (infects rodents, dogs, and humans)
What is the significance of viral spikes in influenza?
They enable the virus to attach and enter host cells.
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