Replication of Viruses Flashcards Preview

RUSVM Virology > Replication of Viruses > Flashcards

Flashcards in Replication of Viruses Deck (57)
1

Nuclear Spread of Virus Genome

Viral genome is integrated into the host cell genome and passed down to next progeny or generation of host cell

2

Assembly and Maturation

Assembly of virus genome and proteins into new virions follows a specific order, all components are packaged to form mature virions

3

Result of splicing

mRNA having different coding information derived from a single gene

4

Burst Size

Number of infectious virions released per average cell

5

Fusion Proteins

Found on the surface of the virus, facilitate membrane fusion

6

Adsorption

During this period, virus attaches to and enters the cells, and the titer of free virus in the medium may actually decline

7

Intercellular Spread

Spread from cell to cell without contact with extracellular environment

8

Replication of (+) single stranded RNA with Reverse Transcriptase

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

9

Exocytosis

Vesicles containing virus migrate to plasma membrane and released

10

Replication of (+) single strand RNA

  • (+)ssRNA → Translates Directly → (+) mRNA → Viral Protein
  • (+)ssRNA → RNA Dependent RNA polymerase → (-)ssRNA
  • (-)ssRNA → RNA Dependent RNA Polymerase → (+) mRNA    → Viral Protein
  • (-)ssRNA → RNA Dependent RNA Polymerase → (+)ssRNA 

11

Mechanisms of intercellular transmission of viruses

Cell to Cell plasma membrane fusion

Passage across tight junction

Movement across a neural synapse

VIral induction of actin or tubulin

Subversion of actin containing structures form filopodial bridges

Membrane nanotube subversion

Virological synapse

12

Monocistronic mRNA

mRNA that encodes one polypeptide

13

Co-Receptor

Additional cell surface molecule required for entry when binding to a cellular receptor is not sufficient for infection

14

Exon

Portion of a gene that encods for amino acids

15

Replication of double stranded RNA

  • (-)dsRNA → RNA Dependent RNA Polymerase → (+) mRNA   → Viral Protein
  • dsRNA → RNA Dependent RNA Polymerase → dsRNA → Viral Genome

16

Pore-Mediated Penetration

Inject their genome into the host cytoplasm throug the creation of a pore in the host membrane 

________________________________

Non-Enveloped Viruses

17

Eclipse Period

Time interval between uncoating (disappearance of viruses) and appearance intracellularly of first infectious progeny virions.

_______________________

No infectious virus can be detected

18

Steps of Virus Replication

Attachment

Penetration

Uncoating

Synthesis of Viral Components

Assembly and Maturation

Release

19

Viral Protein and Nucleic Acid Synthesis

Flow of genetic information in eukaryotic cell

20

Function of the PolyA Tail

Interact with polyA binding protein - translation

21

Splicing

Process that removes introns and joins exons in primary transcript

22

Lysis occurs when a viral capsid induces ruptrue of endosomal membrane, releasing viral capsid or genome in (enveloped/nonenveloped) viruses

Non Enveloped

23

Endocytosis

Process involves invagination and pinching off of small regions of teh cell membrane, resulting in the non-specific internalization of molecules

24

3' Polyadenylation

Stretch of adenylate residues are added to the 3' end

25

Type of Endocytosis that uses specialized lipid rafts

Caveolin-Mediated Endocytosis

26

Extracellular Spread

Released viruses in extracellular environment travel to new cell, same replication cycle occurs

27

Clathrin-Mediated Endocytosis

  • Virion attachment to host cell receptor induces binding of adaptor protein 
  • Adaptor protein bind Clathrin
  • Clathrin-Coated Pit forms
  • Dynamin pinch off Clathrin-Coated Pit from host membrane creating a Clathrin coated vesicle
  • Clathrin basket released from vesicle
  • Vesicle delivers viral components to endosome
  • pH of endosome becomes acidic and viral genome is released

28

Intron

Portion of gene that does not code for amino acids

29

Capping

Additon of 7-methylguanosine to the 5' end of RNA

30

Receptor

Structure on the surface of a cell (or inside a cell) that selectively receives and binds a specific substance and mediates its entry or action into the cell

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