Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Michaelmas Term 1 > The Viruses > Flashcards

The Viruses Flashcards

1
Q

What is a virus?

A

An infectious, often pathogenic agent or biological entity which is typically smaller than a bacterium, which is able to function only within the living cells of a host animal, plant, or microorganism, and which consultants of a nucleic acid molecules surrounded by a protein cost, often with an outer lipid membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Viruses are metabolically

A

Inert

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What do viruses rely on their host cells for?

A
  • energy
  • metabolic intermediates
  • protein synthesis
  • replication environment (obligate intracellular parasites)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the enzymes in a virus mostly geared towards?

A

Infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Virion

A
  • An extracellular virus particle than can move from one cell to another
  • Highly diverse
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What would you use a tissue culture to measure? (Virology)

A

Cytopathic effect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe serology/immunological viral study

A

detection of antibodies to virus in blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Give examples of serology/immunological viral methods

A
  • haemagglutination assay
  • immunofluorescence
  • ELISA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the structure of viruses that infect prokaryote cells

A

Usually have ‘naked’ capsids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the structure of viruses that infect eukaryotic cells

A

Most often enveloped

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the capsid

A
  • one or more protein subunits
  • tightly packed with viral DNA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe virions

A
  • have molecular receptors with varying degrees of complexity
  • enable recognition of, and attachment to, host cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

From where is the envelope derived?

A

The host cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does the envelope cover?

A

Grace he capsid of eukaryotic viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where do most DNA viruses replicate?

A
  • In the nucleus
  • They require host machinery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Where do most RNA viruses replicate?

A

In the cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe group I viruses

A
  • dsDNA
  • must enter cell before replication
  • require host DNA polymerase for genome replication
  • adenoviridae, herpesviridae, papovaviridae
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe group II viruses

A
  • ssDNA
  • most have circular genomes
  • eukaryote viruses replicate in host nucleus
  • parvoviridae (vertebrates), nanoviridae (plants), microviridae (prokaryotes)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe the mechanism by which eukaryote viruses replicate in the host nucleus

A

Rolling circle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe group III viruses

A
  • dsRNA
  • segmented genomes
  • monocistronic replication
  • reoviridae (rotavirus), birnaviridae
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does monocistronic replication mean?

A

One protein produced per gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe group IV viruses

A
  • ssRNA + sense
  • mRNA directly accessed by host ribosomes to form proteins
  • coronaviridae, picornaviridae (Polio)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Group V viruses

A
  • ssRNA -sense
  • genome transcribed by viral polymerases into positive reciprocal sense before translation
  • paramyxoviridae, rhabdoviridae (Rabies), influenza
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Group VI Viruses

A
  • +sense ssRNA replicating through DNA intermediate
  • reverse transcriptase
  • splicing into host genome via integrate
  • replicated using host cell machinery
  • retroviruses (HIV)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Group VII viruses

A
  • dsDNA replicate through ssRNA intermediate
  • viral reverse transcriptase uses progenome RNA to produce DNA
  • hepadna virus (hep B)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Describe the majority of viruses infecting bacteria and archaea

A
  • dsDNA
  • 10-100kb genome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Describe the second largest majority of viruses

A

ssDNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Which type of RNA virus is common in infecting eukaryotic cells

A

+ sense

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Which has greater diversity - eukaryote RNA viruses of prokaryote DNA viruses

A

Eukaryote

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Describe DNA-based
genomes

A
  • less reactive
  • stable in alkaline conditions
  • smaller grooves; more resistant to enzymatic attack
  • mostly ds
  • lower mutation rate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Why are DNA-based genomes less reactive than RNA-based genomes

A
  • deoxyribose less reactive than ribose due to C-H bonds (not C-OH bonds)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Describe RNA-based genomes

A
  • more reactive
  • unstable in alkaline conditions
  • larger grooves; more sensitive to enzymatic attack
  • mostly ss
  • higher mutation rate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

How is phylogenetic analysis conducted on viruses?

A
  • proteome
  • no ribosomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Proteome aka

A

Protein complement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Which appears to be the oldest virus group?

A
  • dsRNA
  • esp. segmented genomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Why might DNA genomes evolve?

A

Protect genomes from cellular ribonuclease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Viroids

A
  • plant pathogens
  • non-protein coding RNA
  • 1/80th size of viruses
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

How is viroid replication mediated?

A

host cell RNA polymerases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Interesting fact about viroids

A
  • highest known mutation rate
  • 1/400 site
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

As genome size increases, mutation rate

A

Decreases (non-linear)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Describe phage latency

A

prophage insertion into host genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What controls the lytic/lysogenic state

A

Genetic switch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What does phage latency allow?

A
  • long-term survival
  • complex interactions of host and phage genomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

When does pseudolysogeny occur?

A
  • nutrient deprivation
  • host cannot support dna replication
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Describe the lytic cycle

A
  1. Phage capsid inserts
  2. Capsid and tail proteins reassemble with phage genome
  3. Assembled phage lyses cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Describe lysogenic state

A
  1. Phage capsid enters
  2. Insertion of phage genome as prophage
  3. Exists in dormant state
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Describe pseudolysogenic state

A
  1. Phage capsid inserts
  2. Phage genome exists as Non-replicating preprophage
  3. Becomes lytic under nutrient rich
  4. Becomes lysogenic under nutrient poor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Mollicutes

A
  • class of bacteria without cell wall
  • Mycoplasma (several pathogenic species in humans and animals)
  • undergo viral budding
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What must happen to gram-negative bacteria before lysis?

A
  • procapsid assembly
  • viral genome packaging
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What must happen to gram-positive bacteria before lysis?

A
  • tail assembly
  • fiber/spike assembly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Instead of lysis, gram-negative bacteria can also exit via

A

Viral extrusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

Describe the generalised eukaryotic virus life cycle

A
  1. Entry
  2. Transcription replication (mediated by viruses vs host défense)
  3. Assembly exit
  4. Virion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

How might an enveloped virion enter a cell?

A
  • attachment and fusion at the plasma membrane
  • endocytosis
  • apoptotic mimicry
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

Describe Virion endocytosis

A
  • reception mediated: clathrin (enveloped only), caveolin, lipid, other
  • macropinocytosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

How might a non-enveloped Virion enter a cell?

A
  • endocytosis
  • Pore-mediated penetration
  • cell to cell transport
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

How might a non-encapsdiated genome enter a cell?

A

Cell to cell transport

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Describe cell to cell transport

A
  • syncytium
  • nanotubules
  • fungus hyphal anastomosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

Describe viral genome replication in eukaryotic cells

A
  • cytoplasmic viral genome can go straight to cytoplasmic transcription and reapplication
  • or nuclear transcription and replication
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

Describe intracellular transport

A

actin-dependent or microtubule-dependent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What must a cytoplasmic viral genome do to undergo nuclear transcription and replication ?

A
  • intracellular transport
  • entry into host nucleus
  • integration into host chromosome
  • latency
61
Q

Which viruses use the peroxysome to replicate?

A
  • tombusvirus
  • spherules
62
Q

Which viruses use the chloroplasm for replication?

A
  • tymovirus
  • spherules
63
Q

Which viruses use the endosome to replicate?

A
  • togaviridae
  • spherules
64
Q

Which viruses use the double membrane vesicles to replicate?

A
  • arteriviridae
  • coronaviridae
  • flaviviridae
  • picornaviridae
65
Q

Which viruses use the endoplasmic reticulum to replicate?

A
  • bromovirus
  • flaviviridae
  • spherules
66
Q

Which viruses use the nucleus to replicate?

A
  • baculoviridae
  • herpesviridae
  • polyomaviridae
67
Q

Which viruses use the mitochondria to replicate ?

A
  • nodavirus
  • spherules
68
Q

Which viruses use the viroplasm (of the mitochondria?) to replicate?

A
  • poxviridae
  • asfaviridae
  • iridoviridae
  • reoviridae
  • filoviridae
69
Q

Which viruses use the Golgi to replicate?

A
  • bunyaviridae
  • Tubes
70
Q

How does virus assembly work if cytoplasmic transcription and replication has occurred?

A
  • cytoplasmic capsid assembly and packaging
  • (can form inclusion body)
  • exit
71
Q

How does virus assembly work if nuclear transcription and replication has occurred?

A
  • nuclear capsid assembly and packaging
  • (can form inclusion body)
  • nuclear exit
72
Q

Describe the 3 methods of virus nuclear exit

A
  1. Nuclear envelope breakdown
  2. Nuclear egress
  3. Nuclear pore export
73
Q

Describe the exit strategy of a non-enveloped virion?

A

Lysis

74
Q

Describe the exit strategy of an enveloped virion

A
  • intracellular transoort
  • budding or cell to cell transport
75
Q

Describe budding

A
  • via ESCRT
  • via ESCRT-independent
76
Q

Describe ESCRT

A

By cellular exocytosis

77
Q

Describe ESCRT-independent

A

At plasma membrane

78
Q

What happens after virion exit?

A

Virion maturation

79
Q

What are segmented RNA viruses?

A
  • retain distinct RNA molecules
  • widespread in nature
  • 11 families
80
Q

Describe the 11 described families of segmented RNA viruses

A
  • dsRNA
  • ssRNA
    • and - sense
81
Q

What happens when two or more compatible viruses infect a cell?

A
  • enable réassortiment and recombination of genomes
  • consequences for evolution and immune escape
82
Q

Describe compatible viruses

A

Influenza

83
Q

Describe the influenza genome

A
  • 8 segments of - sense ssRNA
  • 16H segment and 9N segment subtypes
84
Q

What are H segments

A
  • HA
  • bind to host cell receptors
85
Q

HA

A

haemagglutinin

86
Q

What are N segments

A
  • NA
  • facilitâtes virus exit from host cells
87
Q

NA

A

neuraminidase

88
Q

When do pandemics occur?

A

When viruses with new H types enter the human population by reassortment and interspecies transmission

89
Q

Which strains of influenza are circulating

A
  • H1N1
  • H3N2
90
Q

Which influenza strain disappeared in 2001?

A

H1N2

91
Q

What are the strains of avian flu and what is the pathogenicity?

A
  • H5N2 (low pathogenicity)
  • H5N8 (high pathogenicity)
92
Q

Which station caused the 1918 Spanish influenza and where did it come from)

A
  • H1N1
  • birds
93
Q

Where and how does EBV persist?

A

forms a latent infection persisting in an épuisons of circular DNA within the nuclei of infected B cells

94
Q

EBV

A

Epstein-Barr virus

95
Q

How does EBV spread?

A

Orally; saliva

96
Q

Describe EBV

A
  • dsDNA
  • 172kb genome
  • Herpes family
97
Q

What happens when EBV switches to lytic cycle?

A
  • Death of infected cells
  • sometimes: B cell lymphoma, Burkitt lymphoma, Hodgkin lymphoma and post transplant lymphomas
98
Q

Classical Hodgkin lymphoma is characterised by

A

Atypical EBV associated large tumour cells

99
Q

What causes post transplant lymphomas?

A
  • suppressed T cell responses
  • uncontrolled proliferation of EBV-transformed B cells
100
Q

How does Burkitt lymphoma transformation occur?

A
  • translocation of the MYC oncogene
  • destructive gene mutations
101
Q

ERVs

A

Endogenous retroviruses

102
Q

What percentage of the 3 million transposable elements in the human genome are made up by retroelements

A

90%

103
Q

What are the 2 groups of retroelements?

A
  1. Non-LTR
  2. LTR
104
Q

Describe non-LTR retroelements

A

includes SINE and LINE and processed pseudogenes

105
Q

SINE

A
  • short interspersed elements
  • 80-630bp
106
Q

LINE

A
  • long interspersed elements
  • 6-8kbp
107
Q

Describe LTR

A
  • long terminal repeats
  • includes endogenous retroviruses
108
Q

How does integration of retroelements sometimes cause harm?

A

Disrupting or disregulating essential genes

109
Q

How long is a retrotransposon?

A

4-8kbp

110
Q

How long is an endogenous retrovirus?

A

9-10kbp

111
Q

REV

A

reticuloendotheliosis virus

112
Q

REV can cause

A

Running and tumours in poultry

113
Q

Paleovirology

A
  • the study of ancient viruses
  • detected via accidental insertion into germ line of animal species, becomes EVEs
114
Q

EVEs

A
  • Endogenous viral elements
  • transmitted vertically
  • become ‘fixed’
115
Q

What does it mean for an EVE to be fixed?

A

Present in all members of a species

116
Q

The REV genome is more similar to

A

mammalian retroviruses than to other avian retroviruses

117
Q

What is the reservoir host for Ebola?

A

Bats

118
Q

What is a spillover event?

A

When an animal or human becomes infected with a virus from its reservoir host

119
Q

How is Ebola transmitted from human to human?

A

Contact with blood and body fluid of sick people or Ebola cadavers

120
Q

What percentage of people are asymptomatic for COVID-19?

A

~40%

121
Q

What is the fatality rate for severe COVID?

A

~1%

122
Q

Describe stage I of COVID symptoms:

A
  • fever
  • dry cough
  • diarrhoea
  • headaches
  • loss of smell and/or taste
  • dermal, neurological or cardiac disorders
123
Q

Describe stage II of COVID

A
  • shortness of breath
  • hypoxia
  • coagulation disorder
124
Q

Describe stage III of COVID

A
  • ARDS
  • SIRS/shock
  • coagulation disorder
  • cardiac failure
125
Q

Therapies for COVID

A
  • antiviral drugs
  • reducing immunosuppressive
  • reducing inflammation
  • anti-clotting
126
Q

What does viral shedding indicate

A

Infectiousness

127
Q

Where do the majority of emerging human viruses originate?

A

Other animals

128
Q

What does novel infection emergence depend on?

A
  1. Contact
  2. Mode of transmission
  3. Adaptation to the new species
  4. Human intervention
129
Q

SARS-CoV

A
  • severe acute respiratory syndrome
  • transmission of coronavirus from bats to palm civets to raccoons and ultimately humans
130
Q

Compare and contrast SARS with SARS CoV-2

A

SARS: shedding begins 3 days after symptom onset
SARS CoV-2: shedding begins 3 days before symptom onset

131
Q

Describe the Ebola virus

A
  • filamentous virion
    • sense ssRNA
  • 18-19kb genome, encoding for 7 proteins
  • symptoms appear 2-21 days after infection
  • infects macrophages and epithelial cells
132
Q

Ebola symptoms

A

fever -> unexplained haemorrhaging and bleeding

133
Q

What is the death rate associated with Ebola bleeding and haemorrhaging ?

A

70-80%

134
Q

EBV

A

Ebola virus

135
Q

eVP24

A
  • EBV protein
  • prevents interferon signal (viral destruction)
136
Q

Which is the most fatal Ebola virus?

A

Zaire Ebolavirus

137
Q

How were viruses taxonomically classified back in the day?

A
  • based on biology (informed by phenotypic data)
  • wider host factors
138
Q

When we say virus taxonomy was based on biological classification, what do we mean?

A
  • in vitro properties
  • virion structure
  • antigenic relationships
139
Q

What are the wider host factors for viral classification?

A
  • pathogenicity
  • host range
  • epidemiology
140
Q

How are viruses currently taxonomically classified?

A
  • biological properties
  • sequence relationships (divergence, phylogeny) -> genomic data
141
Q

What is the proposed taxonomy for viruses

A
  • phenotypes inferred from genome analysis
  • sequence relatedness inferred from phylogeny, homologue detection and divergence metrics
  • biological data not essential
  • can be used for virus and metagenomic sequence data
142
Q

APMV

A
  • Acanthamoeba polyphaga mimivirus
  • very large (visible by light microscopy)
  • 1,186kb dsDNA linear chromosome
143
Q

Sputnik

A
  • 50nm icosahedral APMV-associated virus
  • replicates in the virus factory of amoebae co -infected with APMV
144
Q

What is the relationship between Sputnik and APMV?

A
  • Sputnik harms APMV replication
  • 70% reduction in infective APMV particles and threefold reduction in Ameoba lysis at 24hrs after Sputnik infection
145
Q

What is a potential practical problem with tissue culturing?

A

A mono layer of tissue culture cells might curl up

146
Q

Which tissue cells are usually cultured?

A

Sometime human, sometime chicken eggs

147
Q

For a virus to enter a cell it has to

A

Touch it

148
Q

If a virus gets into the nucleus then it has to

A

Get back out again

Michaelmas Term 1 (42 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions