Chapter 6 Flashcards
What is the capsid?
External shell surrounding the virus’s nucleic acids
What types of cells can viruses infect?
Bacteria, algae, fungi, protozoa, plants, animals (all types)
How are viruses referred to?
As infectious particles that are either active or inactive
What are some of the cytopathic effects that can occur?
Disoriented cells, changes in cell shape/size, development of intracellular damage
What are oncogenic viruses?
Viruses that have the ability to cause cancer
What are in vitro methods?
Viral cultivation methods that occur in cell or tissue culture
What is nucleocapsid?
Term referring to the capsid and nucleic acid together
What are spikes?
Projections from the nucleocapsid or envelope that allow viruses to dock with their host cells
What is the genome?
The full complement of DNA and RNA carried by a cell
What are reverse transcriptases?
Enzymes that synthesize DNA from RNA
How were viruses discovered?
By filtering bacteria out of fluid and realizing the fluid was still infectious
What are primary cell cultures?
Freshly isolated animal tissue that is cultured to produce a monolayer with the characteristics of the original tissue
What are complex capsids?
Capsids found in bacteriophages that form unsymmetrical shapes
What is uncoating?
Enzymes in the vacuole dissolve the envelope and capsid, releasing the virus into the cytoplasm
What are capsomeres?
Identical protein subunits that spontaneously self-assemble to form the capsid
What are viroids?
Viruslike agents that parasitize plants and are composed of naked strands of RNA only
What is lysogenic converison?
The acquisition of a new trait from a temperate phage
What are bacteriophages?
Viruses that infect bacteria
What is the virus envelope?
A modified piece of host cell membrane that is found on some, but not all, viruses
What are arenaviruses?
Viruses that pack along host cell ribosomes
What genes do viruses possess?
Only those necessary to invade host cells and redirect their activity
What is negative-sense RNA?
RNA genomes that need to be converted into the proper form to be made into proteins
Why do scientists develop vaccines to viruses as opposed to therapies?
Viruses mutate rapidly, thus making therapy design difficult
What are the characteristics of bacteriophage infections?
Infect every known bacterial species, make bacteria more pathogenic to humans
What are inclusion bodies caused by viruses?
compact masses of viruses or damaged cell organelles in the nucleus or cytoplasm
What is a naked virus?
A virus that consists of only the nucleocapsid
What are in vivo methods?
Viral cultivation methods that occur in lab animals or embryonic bird tissues
What is a virion?
Fully formed virus capable of establishing infection
What are polymerases?
Enzymes that synthesize DNA and RNA
What are prophages?
an inactive state in which phage DNA is inserted into the host chromosome
What is induction?
Activation of a prophage in a lysogenic cell that leads to a lytic cycle
How are enveloped viruses liberated?
Budding or exocytosis
Where do DNA viruses replicate?
Nucleus
What is positive-sense RNA?
Single-stranded RNA genomes ready for immediate translation into proteins
What are satellite viruses?
Viruses that depend on other viruses for replication
What constitutes the informal classification system for viruses?
- Animal, plant, or bacterial virus
- Enveloped or naked
- DNA or RNA
- Helical or Icosahedral
What is the host range?
The range of host cell types that a virus can infect
What are retroviruses?
Viruses that “borrow” the host’s tRNA molecules
What is chronic latent state?
Periodic reactivation after a period of viral inactivity
What is Interferon?
A naturally occurring human cell product that has shown success in preventing and treating viral infections
What happens to a virus during endocytosis?
Entire virus in engulfed by the cell and inclosed in a vesicle or vacuole
What is a lytic cycle?
bacteriophage cycle that ends in bacterial cell destruction
What are temperate phages?
Bacteriophages that can undergo adsorption and penetration but do not immediately undergo replication and release
What are prions?
Distinct protein fibrils found in the brain tissue of animals with encephalopathies
What two parts are every virus formed from?
External coating and core containing nucleic acids
What are the two main capsid shapes?
Helical and Icosahedral
What is a lysogenic cycle?
bacteriophage cycle in which the bacteriophage becomes incorporated into host cell DNA
What are replicases?
Enzymes that copy RNA
What are cytopathic effects?
Virus-induced damage to the cell that alters its microscopic appearance
What are the properties of viruses?
- Not cells and do not fulfill characteristics of life
- Obligate intracellular parasites that rely on host cell for reproduction
- Can have dsDNA, ssDNA, dsRNA, or ssRNA, but not more than one
- Lack enzymes and protein synthesizing machinery
What is adsorption?
The attachment of the virion to the host cell
Where do RNA viruses replicate?
Cytoplasm
What are the general phases in the “life cycle” of animal viruses?
Adsorption Penetration Uncoating Synthesis Assembly Release
What is a provirus?
Virus whose DNA is incorporated into the DNA of the host
What are syncytia?
Fusions of multiple host cells into single large cells containing multiple nuclei
What are the purposes of viral cultivation?
Isolation and identification
Preparation for vaccines
Research
What are plaques?
Clear, well-defined patches in the cell sheet caused by radiating patterns of viral infection
