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TERM 3- Postmidterm > L31, L33- Viruses > Flashcards

L31, L33- Viruses Flashcards

1
Q

individual viral components self-assemble into a….

A

viron

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2
Q

define viron

A

complete infectious form of virus outside of host cell

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3
Q

describe the possible viral genomes

A
  • RNA, DNA
  • ss, ds
  • linear, circular, segmented, haploid, diploid
  • neg/pos sense
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4
Q

viral genome is surrounded by (1), made of viral protein subunits, which will create (2)

A

1- capsomere, capsid

2- nucleocapsid

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5
Q

viruses can be covered by an envelope which originates from (1) and functions to (2); it may also have an additional protein cluster layer termed (3)

A

1- host cell membrane
2- maintains aqueous soln
3- tegument

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6
Q

a viral capsid is made up of one or more (1)s and are held together by (2)

A

1- capsomeres (subunits)

2- non-covalent, reversible hydrophobic or H-bonds

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7
Q

list the general forms of nucleocapsid morphology

A
  • icosahedral
  • helical
  • complex (non-symmetrical)
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8
Q

list the various (4) functions of viral capsid proteins

A
  • define tissue/species specific transmission by interaction with host receptors to facilitate host entry
  • interact with viral nucleic acids for packing/assembling virus
  • assist in viral/host gene regulation
  • evade/block host immune system
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9
Q

describe the components / characteristics of an Isohedral Capsid

A
  • few proteins, 5 protomers form a pentamer
  • limited amt of nucleic acids packaged inside
  • forms independently from genome
  • 5-3-2 axes of symmetry
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10
Q

poliovirus has a ____ capsid

A

icosahedral capsid

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11
Q

describe the components / characteristics of an Helical Capsid

A
  • rod-like filamentous structure
  • capsomeres bind to viral genome (in regular fashion)
  • often ‘open-ended’, form around genome (cannot form empty)
  • contains RNA genomes
  • flexible nucleocapsids wound into ball, surrounded by envelope
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12
Q

rhabdovirus is a _____ capsid

A

helical capsid

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13
Q

bacterophages have a (1) capsids with the following components: (2)

A

1- complex symmetry

2- Head (nucleic acid, protein), Tail / contractive sheath, Tail fibers and pins, Base/End plate

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14
Q

viral envelope is made of (1) derived from (2) via (3) or (4)

A

1- lipoprotein
2- host membrane
3- plasma membrane
4- nuclear, ER, or other internal membranes

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15
Q

viral envelopes are poor in (1) but rich in (2)

A

1- host cell proteins

2- VAP (viral specific glycoproteins - viral attachment protein)

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16
Q

viral envelopes are sensitive to….

A

organic solvents (EtOH, chloroform, ether), detergents, drying, acid, heat

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17
Q

enveloped viruses are usually transmitted by…

A

secretions, large droplets, blood / sexual contact

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18
Q

enveloped viruses usually have a _____ shape

A

spherical or pleomorphic (ability to alter shape)

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19
Q

non-enveloped viruses are sensitive to…

A

nothing, relatively resistant to inactivation by organic solvents, detergents, drying, acid, heat

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20
Q

non-enveloped viruses are usually transmitted by…

A

fecal/oral route, fomites, small droplets

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21
Q

non-enveloped viruses are released by infected cell via…

A

cell lysis

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22
Q

list the viral protein types

A
  • VAP (viral attachement proteins) / peplomers
  • viral polymerase
  • matrix proteins
  • immediate early phase, early phase, late phase proteins
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23
Q

_____ are viral proteins that facilitate host cell entry

A

VAP (viral attachement proteins) / peplomers

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24
Q

list the functions of viral matrix proteins

A

(present between nucleocapsid/envelope)

  • stabilize organization of viral glycoprotein
  • directs viral genome to intracellular sites of viral assembly
  • facilitate virus assembly and budding
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25
Q

after the initial infection of a virus into a host cell, the viral particles disappear in the (1) phase which coincides with (2) period, where (3) occurs; (1) is followed by (4) which ends in the release of viruses

A

1- eclpise
2- latent period
3- viral genome controls host cell protein machinery and directs it to produce viral components
4- maturation

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26
Q

list the stages in viral replication

A

1) attachment
2) penetration
3) uncoating (release of nucleic acids)
4) macromolecular synthesis
5) posttranslational modifications
6) assembly
7) release (lysis of cell or budding out)

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27
Q

list the steps that occur in the Macromolecular Stage of viral replication

A

1) EARLY mRNA and protein synthesis: proteins shut off host cells and replicate viral genome (if needed)
2) replication of genome
3) LATE mRNA and protein synthesis: structural proteins

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28
Q

Early proteins function to (1)

Late proteins function to (2)

A

1- promote viral replication

2- provide structural assistance

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29
Q

what are the 2 possible life cycles of bacteriophages

A
  • Virulent / Lytic phage (kills host following infection)

- Lysogenic / Temperate phage (eventual return to Lytic phage): prophage and integration into host

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30
Q

describe the Lysogenic / Temperate phage

A
  • host is not immediately killed following infection
  • phage genome –> prophage / provirus –> integration in host chromosome or as independent replicating entity equal to that of host genome
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31
Q

define viral tropism and its factors

A

-limitation of virus to single organ / tissue / specialized cell type or a range of any

  • VAPs in outer coat (envelope, capsid) target receptors on host cell (susceptibility)
  • transcription factors allow expression of viral genes
  • Permissivity: cell enzyme pathways to produce viral proteins
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32
Q

list the 2 methods of penetration and uncoating-enveloped viruses

A

1) fusion

2) Endocytosis and acidification

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33
Q

describe fusion as a penetration and uncoating-enveloped viruses technique

A
  • virus glycoproteins attach to host cell receptors
  • envelope-membrane fusion
  • capsid enters, is uncoated, released into cytosol
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34
Q

describe endocytosis and acidification as a penetration and uncoating-enveloped viruses technique

A
  • host cell membrane engulfs virus including envelope
  • capsid is uncoated
  • increased acidity allows viral genome to escape endosome and enter cytoplasm
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35
Q

list the 2 methods of penetration and uncoating non-enveloped viruses

A

1) direct entry across plasma membrane

2) endocytosis

36
Q

describe direct entry across plasma membrane as a penetration and uncoating non-enveloped viruses technique

A
  • virus attaches to host cell receptor
  • sinks into membrane
  • injects genome through pore into the cell
37
Q

describe endocytosis as a penetration and uncoating non-enveloped viruses technique

A
  • virus is engulfed
  • capsule is uncoated
  • viral genome leaves endosome into cytoplasm
38
Q

(T/F) capsid formation always undergoes self-assembly

A

F- some use chaperones to fold the capsomeres

39
Q

viral release occurs through a (1) or (2) mechanism

A

1- exocytosis: capsid uses cell membrane to form envelope laced with viral proteins (more common for enveloped viruses)
2- cell lyses (more common for non-enveloped viruses)

40
Q

describe the two viral enzymes that work against the Central Dogma of Biology

A
  • RNA dependent DNA polymerase (reverse transcriptase): RNA –> DNA
  • RNA dependent RNA polymerase (RNA replicase): neg. sense RNA –> pos. sense RNA
41
Q

describe the features of viral mRNA

A
  • 5’-5’ N7-methylguanosine triphosphate cap

- poly-A tail (100-200 A residues)

42
Q

when viruses replicate in the cytoplasm instead, its mRNA can makes it own 5’ cap or….

A

create 3D RA structure known as Internal RIbosomal Entry Site Element (IRES)

43
Q

list the 4 ways to produce viral proteins via transcription

A
  • individual mRNA for proteins (continuous genome)
  • segmented genome
  • one single long polyprotein –> cleaved into individual proteins
  • frameshift- change reading frame to transcribe individual mRNA/protein
44
Q

in viruses that make long polyproteins, they are cleaved via (1) to make individual proteins, which is a key target for (2)

A

1- proteases

2- viral therapy (protease inhibitors)

45
Q

(1), aka (2) viruses cannot replicate without a helper virus; (3) is a great example

A

1- defective
2- satellite
3- Hep D / HDV

46
Q

describe components of HDV

A
  • ssRNA
  • only infects cells infected by HBV (helper virus)
  • utilizes HBV surface antigen (HBsAg) for entry into host cell
47
Q

10-15% of Prion diseases, aka (1), are developed via (2) mutation on chromosome (3), but most are developed via (4)

A

1- transmissible spongiform encephalopathy
2- Autosomal Dominant
3- chr. 20
4- spontaneous (PrP-c –> PrP-Sc)

48
Q

____virus requires cells undergoing DNA synthesis to replicate

A

parvovirus

49
Q

____virus stimulates cell growth and DNA synthesis

A

papovavirus

50
Q

____virus stimulates cell growth, cell makes RNA intermediate, encodes RNA transcriptase

A

adenovirus

51
Q

____virus stimulates cell growth, encodes its own polymerase and enzymes to provide deoxyribonucleotides for DNA synthesis, establishes latent infection

A

herpesvirus

52
Q

____virus encodes its own polymerases and enzymes to provide deoxyribonucleotides for DNA synthesis, replication machinery, and transcription machinery in cytoplasm

A

poxvirus

53
Q

this group of viruses has (+) RNA genome reseembling mRNA and is transcribed into polyprotein; (-) RNA template is used for replication

A

picornaviruses, togaviruses, flaviviruses, caliciviruses, coronaviruses

54
Q

this group of viruses has (-) RNA genome as template for individual mRNAs and full-length (+) RNA template is required for replication

A

orthomyoxoviruses, paramyoxviruses, rhabdoviruses, filoviruses, bunyaviruses

55
Q

____viruses have (+/-) segmented RNA genome as mRNA template; (+) RNA can be encapsulated to generate (+/-) RNA –> more mRNA

A

reoviruses

56
Q

____viruses have (+) RNA that is converted into DNA and is integrates into host chromatin and transcribed as cellular genes

A

retroviruses

57
Q

briefly define the 7 viral groups via Baltimore Classification

A

I- dsDNA (+/-)
II- ssDNA (+ or -)

III- dsRNA (+/-)
IV- ssRNA (+)
V- ssRNA (-)

VI- ssRNA (+) Retrovirus (has reverse transcriptase)
VII- partial dsDNA (+/-) Retrovirus

58
Q

reverse transcriptase is also known as…

A

RNA dependent DNA polymerase

59
Q

Group I viruses have (+/-) (ss/ds) (DNA/RNA) genomes. They are (non-/enveloped) and replicate in (cytoplasm/nucleus)

A 
1- both +/- strands
2- ds
3- DNa
4- both
5- nucleus
60
Q

Immediate early proteins function to (1). Early proteins then function to (2). Finally, Late proteins function to (3).

A

1- take over cell command
2- target genome replication
3- structural- translocate into nucleus to form capsule

61
Q

HSV is a group __ virus

A

Group I (+/-) dsDNA virus

62
Q

Group II viruses have (+/-) (ss/ds) (DNA/RNA) genomes. They are (non-/enveloped) and replicate in (cytoplasm/nucleus)

A 
1- either +/-
2- ss
3- DNA
4- non-enveloped
5- nucleus
63
Q

Parvovirus is a group __ virus

A

Group II ssDNA virus

64
Q

in Group II viruses ssDNA is converted to dsDNA by (1) and produce virons containing (+/-) sense DNA genome

A

1- host factors and DNA polymerase

2- either pos./neg. sense

65
Q

Group III, IV, V viruses all have (DNA/RNA) genomes and utilize (2) for transcription and replication, skipping (3) intermediates

A

1- RNA genomes
2- RNA-dependent RNA polymerase
3- DNA intermediates

66
Q

only group (III, IV, V) viruses can be translated by host machinery

A

Group IV (+) ssRNA viruses (although replication is still through RNA-dependent RNA polymerase)

67
Q

Group III viruses have (+/-) (ss/ds) (DNA/RNA) genomes. They are (non-/enveloped) and replicate in (cytoplasm/nucleus). Their genome is also termed (6) due to its structure.

A 
1- (+) and (-)
2- ds
3- RNA
4- non-enveloped
5- cytoplasm
6- segmented
68
Q

Rotavirus is a group __ virus

A

Group III (+/-) dsRNA virus

69
Q

Group IV viruses have (+/-) (ss/ds) (DNA/RNA) genomes. They are (non-/enveloped) and replicate in (cytoplasm/nucleus)

A 
1- (+)
2- ss
3- RNA
4- either
5- cytoplasm
70
Q

Poliovirus is a group __ virus

A

Group IV (+) ssRNA virus

71
Q

(+) ssRNA genome has a (1) instead of a cap and is translated into (2)

A

[Group IV]
1- IRES (Internal RIbosomal Entry Site Element)
2- one single long polypeptide (includes RNA-dep. RNA poly.)

72
Q

Group V viruses have (+/-) (ss/ds) (DNA/RNA) (non-/segmented) genomes. They are (non-/enveloped) and replicate in (cytoplasm/nucleus)

A 
1- (-)
2- ss
3- RNA
4- either segmented or continuous
5- non-enveloped
6- cytoplasm
73
Q

Rabes virus is a group __ virus

A

Group V (-) ssRNA virus

74
Q

Group VI viruses have (+/-) (ss/ds) (DNA/RNA) genomes. They are (non-/enveloped) and replicate in (cytoplasm/nucleus)

A 
1- (+) 
2- ss
3- RNA
4- enveloped
5- nucleus
[RETROVIRUSES}
75
Q

HIV is a group __ virus

A

Group VI (+) ssRNA retrovirus

76
Q

what is a provirus

A

when viral genome is integrated into host genome (8% of human genome is from viral origin- possibly tumorigenic)

77
Q

Group VII viruses have (+/-) (ss/ds) (DNA/RNA) genomes. They are (non-/enveloped) and replicate in (cytoplasm/nucleus).

A 
1- (+/-)
2- partial ds (partial ss)
3- DNA
4- enveloped
5- nucleus
78
Q

HBV is a group __ virus

A

Group VII partial (+/-) dsDNA retrovirus

79
Q

why can HBV cause chronic hepatic infection that can lead to hepatocellular carcinoma (HCC)

A

HBV DNA (partial dsDNA retrovirus) integrates into hepatocyte –> which can be tumorigenic in nature

80
Q

HDV is a group __ virus

A

Group V (-) ssRNA virus: requires HBV envelop proteins for infection

81
Q

(T/F) DNA viruses are more stable than RNA viruses

A

T- RNA virus are more error prone and mutate at a faster rate

82
Q

what is complementation of viruses

A
  • 2 viruses infect host cell simultaneously
  • both have defective functions in different gene locations
  • both propagate b/c they can rescue each other’s defective function (complementation)
  • combo progeny virus with no defective functions
83
Q

define Antigenic Drift

A

usually RNA genomes, evolution due to small incremental changes/mutations to genome (slower than Antigenic Shift)

84
Q

define Antigenic Shift

A

usually segemented viruses (notably influenza viruses) exchange RNA segments (reassortment) => highly pathogenic (reassorted) strain virus

85
Q

describe the two types of phenotypic mixing of viruses

A

1) Phenotypic Mixing / Transcapisidation: genome of one virus randomly incorporates into capsid from a different or combination of both viruses
2) Pseudotypes: nucleocapsid of virus acquires envelope from another virus type

86
Q

define viral recombination

A

recombination of viruses infecting the same host- exchanging segments of DNA/RNA (i.e. HSV-1/2)

TERM 3- Postmidterm (11 decks)

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