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biol 459 > Viruses > Flashcards

Viruses Flashcards

1
Q

characteristics of viruses

A
  • obligatory intracellular parasites
  • contain DNA or RNA
  • contain a protein coat
  • no ribosomes
  • no ATP-generating mechanism
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2
Q

____ of diseases are viruses

A

1/3

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3
Q

why can’t viruses use ATP generating mechanisms?

A

they do not have ATPases (important for production of ATP)

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4
Q

what main replicative feature (used to differentiate bacteria) do viruses lack?

A

16S rRNA

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5
Q

which bacteria share certain features with viruses but not other bacteria? what are these features?

A

rickettsias/chlamydias are both intracellular parasites and sometimes require a host for ATP generation

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6
Q

what is meant by ‘host range’?

A

the spectrum of host cells a virus can infect

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7
Q

most viruses infect only _____ of cells in ______

A

specific types, one host

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8
Q

what is the specific types of cells a virus infects determined by?

A

specific host attachment sites and cellular factors (protein-protein interactions)

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9
Q

what are bacteriophages

A

viruses that infect bacteria

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10
Q

what is the size range of a bacteriophage?

A

20nm to 1000nm in length

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11
Q

are bacteriophages specific to a certain type of bacteria?

A

yes

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12
Q

what are the 3 components of a virion (fully developed viral particle)?

A
  • nucleic acid
  • capsid
  • envelope
  • spikes
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13
Q

describe nucleic acid in viral structures

A

DNA or DNA can be single or double stranded, linear or circular

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14
Q

describe capsid in viral structures

A

protein coat made of capsomeres (subunits)

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15
Q

describe envelope in viral structures

A

lipid, protein, and carbohydrate coating on some virsues

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16
Q

describe spikes in viral structures

A

projections from outer surface

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17
Q

do all viruses have an envelope? does influenza virus?

A

no some do not. influenza does though - N protein.

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18
Q

describe the general morphology of viruses

A
  • polyhedral viruses - many sided
  • enveloped viruses
  • helical viruses - hollow, cylindrical capsid
  • complex viruses - complicated structures
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19
Q

viruses must be grown in ___

A

living cells

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20
Q

how are bacteriophages grown in the lab? how can they be recognized?

A

in agar cultures of bacteria. form plaques (clear areas) around bacteriophages on agar surface
-> each plaque corresponds to a single virus; can be expressed as plaque forming units (PFU)

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21
Q

how do we grow viruses in animals?

A
  • embryonate eggs
  • cell cultures
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22
Q

how do we grow viruses in live animals using emyro’s?

A

inject virus into egg and viral growth is signalled by changes or death of the embryo

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23
Q

how do we grow viruses with cell cultures?

A

tissues are treated with enzymes to separates cells
- virally infected cells are detected via their deterioration (cytopathic effect - CPE)
- continuous cell lines are used for the production of vaccine

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24
Q

what are ways to identify viruses?

A
  • cytopathic effects
  • serological tests
  • nucleic acids
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25
Q

what do serological tests include?

A

western blotting - reaction of the virus with antibodies

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26
Q

what does testing nucleic acids include?

A

RFLPs, PCR

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27
Q

for viruses to multiply…

A
  • must invade a host cell
  • must take over the hosts metabolic machinery
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28
Q

what does the viral one step growth curve include

A
  • eclipse period
  • virions released from host cell
  • acute infection
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29
Q

describe the eclipse period of a viral infection

A

the period while the virus is replicating in the cell and before mature virions are released

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30
Q

describe the acutre period of viral infection

A

when virion release from the cell ramps up and before the immune response takes over

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31
Q

what are the two types of cycles for multiplication?

A
  • lytic cycle
  • lysogenic cycle
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32
Q

what is the difference between the viral lytic cycle and a viral lysogenic cycle?

A

lytic: phage causes lysis of cell upon rpelication
lysogenic: phage DNA incorporated into host DNa and replicates normally

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33
Q

what 5 mains steps outline the viral lytic cycle?

A
  1. attachment
  2. penetration
  3. biosynthesis
  4. maturation
  5. release (lysis)
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34
Q

what happens during attachment?

A

phage attaches by the tail fibers to the host cell

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35
Q

what happens during penetration?

A

phage lysozyme opens the cell wall; tail sheath contracts to force the tail core and DNA into the cell

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36
Q

what happens during biosynthesis?

A

production of phage DNA and proteins

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37
Q

what happens during maturation?

A

assembly of phage DNA and proteins

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38
Q

what happens during release?

A

phage lysozyme breaks the cell wall

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39
Q

what lysogeny

A

phage remains latent

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40
Q

what term is used to describe the inserted phage DNA before it becomes a new virion?

A

a prophage

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41
Q

describe the lysogenic cycle

A
  • phage DNA incorporates into host cell DNA
  • when the host cell replicates its chromosomes, it also replicates prophage DNA
  • results in phage conversion
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42
Q

whats phage conversion?

A

the host cell exhibits new properties

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43
Q

what is meany by ‘specialized transduction’ with regards to bacterial/viral reproduction?

A

when a bacteria takes advantage of a phage to spread its genes to other bacteria for reproduction

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44
Q

what does specialized transduction result in?

A

changes genetic properties of the bacteria

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45
Q

viral genus names end in ____

A

-virus

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46
Q

viral family names end in ___

A

-viridae

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47
Q

viral order names end in ____

A

-ales

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48
Q

definition of a viral species?

A

a group of viruses sharing the same genetic info and ecological niche (host)

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49
Q

what must a virus also have if it carries its genetic material as RNA?

A

reverse transcriptase

50
Q

what must a virus also have if it carries its genetic material as DNA?

A

regular transcriptase (polymerase)

51
Q

where in a bacterial cell does viral infection occur? what about euk cells?

A

bacteria: cytosol
euks: cytosol or nucleus

52
Q

what are two way viruses can enter into host cells?

A

receptor mediated endocytosis
fusion

53
Q

what virus enters via receptor mediated endocytosis?

A

pig retrovirus

54
Q

what virus enters by fusion?

A

herpesvirus

55
Q

DNA viruses ____ their DNA in the _____ of the host using _____

A

replicated, nucleus, viral enzymes

56
Q

in the biosynthesis of DNA viruses, they synthesize _____ in the ____ using host cell _____

A

capsid, cytoplasm, enzymes

57
Q

how are enveloped viruses released from the cell? non enveloped viruses?

A

enveloped: budding (endocytosis)
non: lysis

58
Q

what kind of genome do class I viruses have?

A

dsDNA

59
Q

examples of class I viruses

A

smallpox (poxviridae), chickenpox (herpesviridae), adenoviridae, herpes simplex, epsterin-barr

60
Q

what 2 notifiable diseases belong to class I (dsDNA viruses)?

A
  1. small pox - poxviridae
  2. chickenpox - herpesviridae
61
Q

what does adenoviridae cause in humans? animals?

A

respiratory infections in humans, and tumors in animals

62
Q

what has adenoviridae been used for?

A

used for development of astrazeca vaccine against covid 19

63
Q

is adenoviridae enveloped or non?

A

is a dsDNA nonenveloped

64
Q

what kind of virus is poxviridae?

A

dsDNA, enveloped

65
Q

what symptom does poxviridae cause?

A

skin lesions

66
Q

what are some examples of poxviridae?

A

smallpox, variola virus, vaccinia, cowpox, monkeypox, camelpox

67
Q

what is the origin of vaccinia?

A

unclear, no one knows for sure

68
Q

why is it important for the variola virus genome to have inverted tandem repeats at both ends? how are these sometimes activated?

A

to enable circularization/insertion. sometimes triggered by UV light

69
Q

what kind of virus is herpesviridae?

A

dsDNA enveloped

70
Q

list the examples of herpesviridae

A

HHV-1 Simplexvirus
HHV-2 Simplexvirus
HHV-3 Varicellovirus
HHV-4 Epstein-Barr virus
HHV-5 Cytomegalovirus
HHV-6 Roseolovirus
HHV-7 Roseolovirus
HHV-8 Rhadinovirus

71
Q

what does HHV-1 and HHV-2 causes?

A

cold sores and conjunctivitis

72
Q

what does HHV-3 - varicellovirus cause?

A

chicken pox, is notifiable

73
Q

what does HHV-4 causes?

A

lymphocryptovirus; causes mononucleosis (epstein barr virus)

74
Q

what does HHV-8 cause?

A

rhadinovirus; causes kaposi’s sarcoma (cancer)

75
Q

what kind of virus is papovaviridae?

A

dsDNA, nonevloped

76
Q

what is an example of papoviridae?

A

papillomavirus

77
Q

what does papillomarvirus cause?

A

warts, can transform cells and cause cancer

78
Q

how can HPV be implicated in cancer development?

A

because one of its early genes binds to p53, a well known oncogene

79
Q

what accounts for class II viruses?

A

ssDNA viruses ->few human animal disease and no notifiable dz

80
Q

what is an example of a ssDNA virus?

A

parvovirus b19

81
Q

what does parvovirus b19 causes

A

is a childhood dz giving a red skin rash

82
Q

what is an example of partial dsDNA virus?

A

hepatitis b virus, can cause jaundice

83
Q

hepadnaviridae uses ____ to make ___ from ___

A

reverse transcriptase, DNA,RNA

84
Q

virus multiples in the host cells ____ using ____

A

cytoplasm, RNA-dependent RNA polymerase

85
Q

What differentiates ssRNA (+) from ssRNA (-)?

A

(+): sense, RNA acts as mRNa and is translated directly.

(-): antisense, transcribed to + strand before translation.

86
Q

are reoviridae viruses notifiable?

A

no

87
Q

what is an example of dsRNA virus?

A

rotavirus, causes infant dha

88
Q

what are two examples of reoviridae?

A

reovirus, rotavirus

89
Q

what are the notifiable dz’s of ssRNA (+)?

A
  • Poliomyelitis (Picornaviridae)
  • HepatitisA (Picornaviridae)
  • HepatitisC (Flaviviridae)
  • WestNileVirus (Flaviviridae)
  • YellowFeverVirus (Flaviviridae)
  • Rubella( Togaviridae)
  • Norovirus(Norwalk)
  • SARSCoV-1(Coronaviridae)
    -SARS CoV-2 (Special database for Covid-19)
  • MERS (not notifiable in Canada)
90
Q

what is picornaviridae?

A

ssRNA, + strand, nonenveloped, no membrane

91
Q

examples of picornaviridae

A

enterovirus, rhinovirus, hepatitis A

92
Q

what is an example of an entervirus?

A

poliovirus and coxsackievirus

93
Q

what does rhinovirus cause

A

common cold

94
Q

when looking at poliovirus, it is noted there is a poly-a tail. why is this important?

A

it is involved in protein synthesis in euks, implies virus may be derived from euks

95
Q

what are togaviridae?

A

ssRNA + strand, enveloped virus

96
Q

what are the two genera of togaviridae?

A
  1. alphavirus
  2. rubivirus
97
Q

alpha virus

A

transmitted by arthropods, includes chikungunya

98
Q

example of rubivirus

A

rubella

99
Q

what is rubella congenital syndrome

A

serious dx of fetus: possible blindness or mental retardation

100
Q

What 3 viruses are countered by the MMR vaccine given to children? What genotype does it target?

A
  • Measles
  • Mumps
  • Rubella
    Target A genotype, though effective against some others.
101
Q

what are flaviviridae?

A

ssRNA, + strand, enveloped viruses

102
Q

3 examples of viruses belonging to flaviviridae

A
  1. hepatitis c
  2. west nile virus
  3. yellow fever virus
103
Q

how is hep c transmitted?

A

blood, sex, mother to infant, needles

104
Q

how are west nile virus and yellow fever virus transmitted?

A

by arthropods

105
Q

norovirus

A

ssRNA + strand viruses

106
Q

example of notifiable norovirus

A

norwalk virus

107
Q

norwalk virus

A

cause GE which includes diarrhea and vomiting
- can affect all age groups
- more common in winter

108
Q

coronaviridae examples

A

SARS Cov1, SARS Cov2, MERS

109
Q

SARS cov1

A

(Severe Acute Respiratory Syndrome Coronavirus 1)
* Origin in China in January 2003. Outbreak in Canada. early 2003 (Toronto). CFR about 10%. Bats and civets as original host.

110
Q

SARS Cov2

A

(disease is Covid-19)
* Origin in China in December 2019. Outbreak worldwide in 2020.
CFR about 1%. Bats likely the original host, but unclear still.

111
Q

MERS

A

Middle East Respiratory Syndrome
* Origin in Saudi Arabia 2012 but has spread to several countries including the USA. CFR 36%. Camels likely the original host. No cases reported in Canada. No specific vaccine or treatments. 2519 cases between 2012 and 2020.

112
Q

MERS and SARS relation

A

evolved from a distant ancestor: helps us design vxn and control spread of dz

113
Q

what is used as target for vaccine in SARS cov2?

A

spike protein w/ receptor binding domain

114
Q

what is used by BC CDC for genotyping on SARS cov2?

A

RdRp: RNA dependent RNA polymerase

115
Q

ssRNA - strand notifiable dz’s

A
  • InfluenzaVirus
  • Rabies
  • Measles
  • Mumps
  • Hantavirus pulmonary syndrome
  • Hemorrhagic fever (Ebola,Marburg)
116
Q

example of orthomyxoviridae

A

influenza A virus: segmented genome

117
Q

rhabdoviridae

A

ssRNA - strand, envloped viruses

118
Q

example of rhabdoviridae

A

rabies

119
Q

2 examples of paramyxoviridae

A
  • measles virus (morbillivirus)(vxn preventable)
  • mumps (rubulavirus)(vxn preventable)
  • both are class V ssRNA -
120
Q

what is the difference in measles and mumps genomic structure?

A

mumps has SH, HN, and V/P

121
Q
A

biol 459 (9 decks)

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