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RUSVM Virology > Replication of Viruses > Flashcards

Flashcards in Replication of Viruses Deck (57)
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31

Alternative Splicing

All introns spliced out, only select exons spliced in

32

Latent Period

Time before new infectious virus appears in the medium

_________________________

No extracellular virions detected

33

pH Independent Fusion Proteins

  • Fusion protein catalyzes membrane fusion at the cell surface at neutral pH
  • Viral nucleocapsid is released into the cytoplasm

34

Functions of the 5' Cap

Adds stability to the mRNA

Binding of mRNA to ribosomes

Marks mRNA as self

35

Permissive Cell

Cell in which a virus is able to replicate

36

Replication of (-) single strand RNA

  • (-)ssRNA → RNA Dependent RNA Polymerase → (+) mRNA    → Viral Protein
  • (-)ssRNA → RNA Dependent RNA Polymerase → (+) ssRNA → RNA Dependent RNA Polymerase → (-)ssRNA → Viral genome

37

Non-Permissive Cell

Cells in which a factor or factors necessary to viral replication is not present or one detrimental to viral replication is present

38

Surface Fusion

Enveloped virus fuses with the surface of the host cell, the viral glycoproteins are retained on the cell surface and since they are antigenic the cell becomes a target for immune response

39

Antibody Mediated Penetration

  • Virus enters the macrophage by attachment of its spike proteins to the CD13 receptor
  • Antibodies against spike protein cannot clear the virus from the host  - antibodies bind to spike proteins and facilitate entry of virus into host cell through IgG-Fcy receptor

40

Replication of single stranded DNA

  • (+)ssDNA Strand → DNA-Dependent DNA Polymerase → dsDNA Intermediate
  • (-)dsDNA Intermediate → DNA Dependent RNA Polymerase → (+) mRNA → Viral Protein
  • (-) dsDNA Intermediate → DNA-Dependent DNA Polymerase → (+)ssDNA → Viral Genome 

41

Enveloped virions release progeny virions by 

Budding

42

Replication of double stranded DNA with Reverse Transcriptase

  • dsDNA → (+) ssRNA → RNA dependent DNA polymerase      → (-)ssRNA → DNA dependent DNA polymerase → (-) dsDNA → DNA dependent RNA polymerase → (+)mRNA → Viral Protein 

43

Enveloped viruses can penetrate the host cell by 

Surface Fusion

44

Antibody Dependent Cell Mediated Cytotoxicity

  • Antibody binds antigens on the surface of the target cell
  • Fc receptors on NK cell recognize bound antibody
  • Cross-linking of Fc receptors signals the NK cell to kill the target cell 
  • Target cell dies by apoptosis

45

T/F: Viruses multiply by division

False

___________________________

Viruses do not have the genetic capability to muliply by divison

46

Naked Virions release progeny virions by

Lysis of host cell

47

Uncoating

Release of viral genome in host cell

48

Polycistronic mRNA

mRNA that encodes several polypeptides

49

Some (enveloped/nonenveloped) viruses induce local permeabilization of host endosomal membrane to allow virus capsid penetration into the cytoplasm

Non Enveloped

50

Penetration of the virus into the host cell typically occurs by

Endocytosis

51

pH Dependent Fusion Proteins

  • Low pH in endosome promotes fusion of envelope with endosomal membrane
  • Lysis of nucleocapsid by lysosomal proteases and release of viral genome

52

Replication of double stranded DNA viral genome

  • (-)dsDNA Strand → DNA-Dependent RNA Polymerase → (+) RNA → Viral Protein
  • (+) and (-) dsDNA Strand → DNA-Dependent DNA Polymerase → dsDNA → Viral Genome 

53

Constitutive Splicing

Every intron is spliced out and every exon is spliced in

54

Surface membrane fusion of enveloped viruses results in

Antibody-Dependent Cell Mediated Cytotoxicity

55

Assembly and Maturation can take place in 

Nucleus, Cytoplasm or Plasma/Cell Membrane

56

Fusion of virus membrane with host endosomal membrane releases the viral genome in (enveloped/nonenveloped) viruses

Enveloped

57

Caps are synthesized from what sources

Host Cell Enzymes

Viral Enzymes

Cap Snatching - from host mRNA