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BASI EXAM 7: Viruses
Terms in this set (44)
Latin for "poison"
What does the name "virus" come from?
1. obligate INTRACELLULAR
2. non-cellular= NOT ALIVE
3. reproduce within living cells only; NO BINARY FISSION
4. NO independent metabolism (get energy and precursors from host)
Give some general characteristics of viruses
1. latent period: building up components of virus
2. rise: rapid replication
3. yield (burst size)= viral eruption
This is the type of growth curve viruses have
-INDIRECT detection is important, this is what's used clincally
what type of microscopy can see viruses?
EITHER DNA or RNA, NOT BOTH
explain the nucleic acids contains in viruses
nucleic acid encapsulated by an envelope or rigid structure
explain the simple structure of viruses
FROM INNER TO OUTER
1. nucleic acid core
2. capsid w/ capsomeres
4. spike (peplomeres)
describe the "average" structure of a virus
small repeating subunits of proteins that form viral capsid
what is a capsomere?
the complete and infection virus particle
what is a virion?
composed of repeating capsomeres
protein covering surrounding core of nucleid acid (and sometimes enzymes)
what is a capsid?
membrane-like outer covering of SOME viruses "stolen" from host
-when virus exits host, the host membrane is studded w/ viral proteins
describe a viral envelope
1. extended nucleic acid form
2. condensed nucleic acid form
What are the two ways that proteins associate with the viral genome?
viral proteins embedded in envelope
describe viral spikes (peplomeres)
linear, single molecules
can be ds, ss, segmented
most viral genomes are _________ but can be ____
(+) RNA = virus RNA genomes are mRNA and are directly translated by host cell
(-) RNA= first must be transcribed before translation
-both must bring in RNA dependent RNA polymerase because host cell doesn't have
Define RNA virus polarity
1. physical features
2. biological properties
Viruses are classified by these two major qualities
capsid is helical shaped
capsid is icosahedral shaped
what are the two structural forms of viruses?
what is the structure of this capsid?
what is the structure of this capsid?
rapid replications at expense of host cell!
what is the goal of all viruses?
viruses are never considered ______ but ideas on this are in flux
2. latent period
3. burst/release of progeny virus
what are the three stages of viral replication?
1. uncoated w/ envelope if present
2. capsid removed
3. virus genome exposed
4. virus begins to be built
what happens during the latent period of viral replication?
early= DNA synth
late= capsid proteins
what are the early genes in viral replication? late?
typically w/in HOST NUCLEUS
1. disrupt p53 and RB to push host to S phase (inhibit replication checkpoints)
2. express host-independent DNA replication functions
Explain the strategy of DNA Viruses and where they typically replicate
typically w/in HOST CYTOPLASM
1. (+)RNA: synthesize all needed enzymes in host
2. (-)RNA: RNA-dep RNA polymerase is carried into host cell in capsid
Explain the strategy of RNA Viruses and where they typically replicate
1. convert "pseudo-diploid" RNA genome to DNA= REVERSE TRANSCRIPTION= RNA-DEPENDENT DNA POLYMERASE
2. integrate DNA into host genome as "PROVIRUS"
Explain the strategy of Retroviruses
virus elect to not instantly kill cell
-stable, long-term associations b/ween host and virus
-gives host chance to replicate for new viable virus locations
What are non-lytic interactions?
1. acute: multiply rapidly until host immune functions stop activity or die
2. persistent: virus= long-term resilience w/in host
*still can be transmitted to other hosts
What are the two major types of viral infections?
What are the three types of persistent infections?
intermittent acute episodes of clinically evident virus production then disappearance of clinical signs/symptoms
What are latent infections?
herpes simplex in cornea
what is this disease?
virus is constantly present at detectable levels but signs and symptoms ebb and flow
what are chronic infections?
what type of infection does Herpes yield?
what type of infection does HepB yield?
virus induce changes in host cell to become MALIGNANT
what are transforming infections?
transforming= cervical dysplasia/cancer
what type of infection does HPV yield?
CPE, when viruses physically modify infected host cells in a visible way
What are cytopathic effects?
1. inclusion bodies (sites of replication of viruses)
2. syncytia formation (multi-nucleated giant cells)
what are the two major cytopathic effects (CPEs) of viruses?
most have line of host cells to grow or grown within organism
how do you culture viruses?
avoidance of infection in the first place
the most successful approach to control viral infection is
1. quarantine and public health
2. vaccination (active and passive)
3. barriers ("cover your mouth")
4. antiviral agents (rare)
list the common prevention methods for viral infection
a new agent or an expansion beyond usual range, or an increase in virulence
what is an emerging infection?
ebola in 2014-2019
the largest outbreak ever was the outbreak of _____
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