L 26 - 30 Flashcards
True or False: Viruses are obligate intracellular parasites that use host cell translation machinery
True
Viral replication yields ___, which are the vehicle for transmission to next host cell
Virion
True or False: Viral genome is RNA only and are packaged inside particle
False - while genomes of viruses are packaged inside particle, the genome itself can be RNA/DNA
DNA viruses either use host ___ or encode their own
polymerases
True or False: (+) SS RNA viruses makes mRNA while – transcription/translation–(-) SS RNA makes polypeptides only
False
(+) SS RNA
- polyproteins
- translation
(-) SS RNA
- mRNA
- proteins
Which of the following must encode RNA-dependent polyermase?
A. (+) SS RNA
B. (-) SS RNA
B. (-) SS RNA
_____: (+) sense RNA viruses that require DNA intermediate for replication (RNA to DNA to RNA)
A. Hep B Virus
B. Retrovirus
C. Hep C Virus
Retroviruses
_____: A gapped DNA genome; full-length but nicked (+) strand and partial (-) strand
A. Hep B Virus
B. Retrovirus
C. Hep C Virus
A. Hep B Virus
What are four mechanisms used to get many proteins out of small genomes?
- polyprotein synthesis
- leaky scanning
- ribosomal binding sites
- inefficient start codon - reinitiation
- many upstream ORF - many ribosome binding sites
____: secondary structure that is important for efficient recognition of mRNA and translation
____: promotes packing of genome for assemebly into developing virions
IRES; packaging signals
True or False: Capsids can be Icosahedral or Helical
True
All humans with helical symmetry are ____
No DNA viruses have been discovered that are helical
enveloped
True or False: Enveloped viral envelopes take part of the plasma membrane with them, whereas non-enveloped leave cell without any host plasma membrane
True
Why are enveloped viruses wimpy?
- Envelopes break down fast outside of host
Which are harder to destroy: enveloped or non-enveloped viruses?
Non-enveloped – because they have stable capsid protein
____: Occurs after attachment; time between entry and production of new virus
____: Number of viruses undergoes exponential growth
A. Eclipse; Exponential
B. Exponential; Eclipse
A. Eclipse; Exponential
Three steps of viral infection?
- Attach, penetrate, and uncoat
- Transcription, translation, and replication
- Viral assembly, exit, and maturation
What are the three mechanisms for viral entry? Which is NOT pH dependent?
1) Uncoating at plasma membrane
- pH Independent
- No endosomal acidification
2) Uncoating within endosomes
3) Uncoating at nuclear membrane
A viral genome may or may not encode its own polymerase but no virus encodes its own ___ machinery. Thus, all viruses depend on host to make proteins
transcriptional
Which three places can viral assembly occur?
- Nucleus
- Herpes - Cytoplasm
- Vacina - Cell membrane
- Retrovirus
How do non-enveloped viruses leave the cell?
How do enveloped viruses leave the cell?
Non-enveloped = Lysis
Enveloped = Budding
Which type of infection involves a non-permissive cell and a defective infecting virus? Ultimately, the host cell dies before virus is even made (no viral progeny made!)?
A. Persistent Infection
B. Abortive Infection
C. Latent Infection
B. Abortive Infection
Which type of infection allows viruses to constantly be made, with host cell maintaining normal function?
A. Persistent Infection
B. Abortive Infection
C. Latent Infection
A. Persistent Infection
True or False: In a latent infection, host cell survives and no virus is made, but some viral proteins are. Can be reactivated to make virus!
True
True or False: In oncogenic transformation, cells are immortalized
True
Abortive and Latent infections have ___ effect while___ infections cause senescence and cytolytic infections cause cell death
Abortive/Latent: no
Persistent: senescence
Cytolytic: cell death
What do you need to make a productive infection?
- Enough virus
- Permissive cells at infection site
- Absent local host defenses
Lymphatic spread is an example of ___ infection
systemic
How can viruses disseminate throughout body???
1) Lymphatics
2) Blood
3) Neurally
True or False: Virus must be grown in vitro
False - in cell culture
Three tests for detecting viruses?
1) Direct
- examined?
2) Indirect
- Specimen is incubated in presence of cells that allow for growth
3) Serology
- Ab titer against antigen
Electron/Light microscopy, Antigen detection, and molecular techniques are example of ___ virus examination
direct
Two steps to indirectly examining virus?
Step 1: cell culture
- primary cells (normal)
- semi-cont (embryonic)
- conti (immortal)
Step 2: presence of virus detected by
- tzanck smear
- cytopathic effect
- haemadsorption
True or False: Serology is used to diagnose a primary infection
True
Which two are acute infections?
A. HPV and HIV
B. HPV and Measles
C. Flu and Measles
C. Flu and Measles
True or False: HIV can either be a persistent/chronic infection or a slow, viral infection
True
True or False: HPV is a tumor related virus
True
Which two serotypes are important in influenza?
A. A and B
B. B and C
C. C and D
A. A and B
True or False: Orthomyxovirus can cause the flus - it is ENVELOPED, SEGMENTED, (-) ssRNA that is helical
True
Serotypes in influenza are based on M_ and M_
M1 (nucleocapsid protein)
M2 (membrane protein)