9.4 LAST PART INTRO Flashcards
1
Q
What is the most widely used technique to resolve fine differences in viral morphology
A
Electron microscopy
2
Q
What stain is used in electron microscopy for viruses
A
Potassium Phosphotungstate
3
Q
What technique involves quick freezing in vitreous ice
A
Cryoelectron microscopy
4
Q
What technique is used for small nonenveloped viruses
A
X-ray diffraction
5
Q
What is the pattern of cubic symmetry observed in animal viruses
A
Icosahedral pattern
6
Q
How many faces does an icosahedral pattern have
A
20
7
Q
How many vertices are present in an icosahedral pattern
A
12
8
Q
What type of axes of rotational symmetry are found in an icosahedral pattern
A
Fivefold threefold and twofold
9
Q
What shape do most viruses with icosahedral symmetry have
A
Spherical
10
Q
What binds protein subunits to viral nucleic acid in helical symmetry
A
A periodic interaction
11
Q
Where is the nucleocapsid coiled in animal viruses with helical symmetry
A
Inside a lipid-containing envelope
12
Q
What type of genome do all animal viruses with helical symmetry contain
A
RNA genomes
13
Q
Which virus has a rigid nucleocapsid and a bullet shape
A
Rhabdovirus
14
Q
Which virus has a complex structure and is brick-shaped with ridges
A
Poxviruses
15
Q
What is the most widely used method for measuring virus sizes
A
Direct observation in electron microscope
16
Q
What method measures virus size based on sedimentation rate
A
Sedimentation ultracentrifugation
17
Q
What is the size range of viruses
A
20nm-300nm
18
Q
What is the size range of bacteriophages
A
10nm-100nm
19
Q
What is the size of Staphylococcus bacteria
A
1000nm
20
Q
What is the smallest RNA virus
A
Picornavirus
21
Q
What is the smallest DNA virus
A
Parvovirus
22
Q
What facilitates the transfer of viral nucleic acid between host cells
A
Virus protein
23
Q
What protects the viral genome against inactivation by nucleases
A
Virus protein
24
Q
What participates in the attachment of a virus particle to a susceptible cell
A
Virus protein
25
What determines the antigenic characteristics of a virus
Virus protein
26
What process exposes nucleic acid to initiate viral replication
Uncoating
27
What encodes genetic information necessary for viral replication
Viral nucleic acid
28
What are the possible forms of viral nucleic acid strands
Single or double stranded circular or linear segmented or nonsegmented
29
On what basis are viruses classified into families
Type of nucleic acid strandedness and size
30
What is the size range of viral DNA genomes
3.2 kbp to 375 kbp
31
Which virus has the smallest DNA genome at 3.2 kbp
Hepadnavirus
32
Which virus has the largest DNA genome at 375 kbp
Poxviruses
33
What is the size range of viral RNA genomes
4 kb to 32 kb
34
Which virus has the smallest RNA genome at 4 kb
Picornavirus
35
Which virus has the largest RNA genome at 32 kb
Coronavirus
36
What is the origin of viral lipid envelopes
Acquired during budding through cellular membranes
37
What determines the specific phospholipid composition of a virion envelope
The type of cell membrane involved in budding
38
What is the effect of ether on lipid-containing viruses
Sensitive and inactivated
39
What is the effect of ether on non-lipid containing viruses
Resistant
40
What are viral glycoproteins primarily involved in
Attachment to target cells and membrane fusion
41
What role do envelope glycoproteins play in the immune response
They serve as viral antigens and interact with neutralizing antibodies
42
What technique provides insights into the structure of viral glycoproteins
X-ray crystallography
43
What are the three basic types of cell cultures used for virus cultivation
Primary secondary and continuous cell lines
44
What is primary culture made from
Dispersed cells from freshly removed host tissues
45
What is a limitation of primary cell cultures
Unable to grow for more than a few passages
46
What type of cell lines are secondary cultures
Diploid cell lines
47
What is a characteristic of secondary cell cultures
Retained normal chromosomal patterns
48
What type of cells are continuous cell lines derived from
Cancer cells or malignant tissue
49
What is a characteristic of continuous cell lines
Capable of prolonged growth with altered chromosomal patterns
50
What method is not used for virus cultivation
Agar
51
How can viral replication be monitored
Cytopathic effects appearance of virus-encoded proteins detection of virus-specific nucleic acid hemadsorption and viral growth in embryonated chick eggs
52
What is cytopathic effect
Cell lysis necrosis inclusion formation giant cell formation and cytoplasmic vacuolization
53
What is an example of cytopathic effect in CMV
Inclusion formation
54
What is hemadsorption
Adsorption of erythrocytes to infected cells
55
What is the result of viral growth in an embryonated chick egg
Death of the embryo production of pocks or plaques and development of hemagglutinins
56
What type of virus causes rapid rounding of cells progressing to complete cell destruction
Enterovirus
57
What type of virus causes focal areas of swollen rounded cells
Herpesvirus
58
What type of virus causes focal areas of fused cells
Paramyxovirus
59
What is inclusion body formation
Site of virion development often larger than individual virus particles and may stain with acid dyes
60
Where can inclusion bodies be located
Nucleus cytoplasm or both
61
What is the diagnostic significance of inclusion bodies
Presence aids in diagnosis
62
What type of inclusion bodies are associated with rabies virus
Negri bodies
63
What type of inclusion bodies are associated with yellow fever virus
Torres Councilman bodies
64
What type of inclusion bodies are associated with fowlpox
Bollinger bodies
65
What type of inclusion bodies are associated with variola and varicella
Guarnieri-Paschen bodies
66
What type of inclusion bodies are associated with ectromelia
Marshall bodies
67
What type of inclusion bodies are associated with herpes zoster
Multinucleated giant cells and intracellular inclusions
68
What is the most widely used method for quantifying viral nucleic acids
PCR
69
What are serologic tests used for virus quantitation
RIA and ELISA
70
Which assay is easy and rapid for virus quantitation
Hemagglutination assay
71
What physical method involves direct visualization of virions
Electron microscopy
72
What is the basis for endpoint biologic assays
Animal death infection or cytopathic effects at serial dilutions
73
How is titer expressed in endpoint biologic assays
As ID50 reciprocal of the dilution producing effects in 50% of cells or animals inoculated
74
Which assay is widely used for infectious viruses that grow well in tissue culture
Plaque assay
75
What does immunofluorescence detect in infected cells
Viral antigens
76
Which viruses form pocks on the chorioallantoic membrane of embryonated eggs
Herpes and Vaccinia viruses
77
What is the first step in virus purification
Concentration of virus particles using precipitation ultrafiltration or hemagglutination and elution
78
How are orthomyxoviruses concentrated during purification
Hemagglutination and elution
79
What methods are used for separating virus particles from host materials
Differential centrifugation density gradient centrifugation column chromatography and electrophoresis
80
What criteria must be met to identify a particle as a virus
Obtained only from infected cells identical from various sources contains nucleic acid distinct from host cells infectivity correlates with particle count destruction leads to loss of activity reacts with antisera induces characteristic disease produces progeny with identical properties in tissue culture
81
What are common hazards in the laboratory
Aerosols ingestion skin penetration and splashes into the eye
82
What activities produce aerosols
Homogenization centrifugation ultrasonic vibration and broken glassware
83
What activities can lead to ingestion of infectious agents
Mouth pipetting eating smoking or inadequate hand washing
84
What causes skin penetration hazards
Needle sticks broken glassware leaking containers handling infected tissues or animal bites
85
What precautions should be observed in the laboratory
Standard precautions
86
What are good biosafety practices
Training in aseptic techniques prohibition of mouth pipetting no eating drinking or smoking use of PPE sterilization of experimental wastes use of biosafety hoods and immunization if vaccines are available
87
Which viruses are stable at 37°C for several hours
Icosahedral viruses
88
Which viruses are more heat labile
Enveloped viruses
89
At what temperature and duration is viral infectivity destroyed
50–60°C for 30 minutes
90
Which viruses are exceptions to heat destruction at 50–60°C
Hepatitis B virus and Polyomavirus
91
Why are prions resistant to heat destruction
Due to their unique structure
92
Which salts stabilize picornaviruses and reoviruses
MgCl2 at 1 mol/L
93
Which salts stabilize orthomyxoviruses and paramyxoviruses
MgSO4 at 1 mol/L
94
Which salts stabilize herpesviruses
Na2SO4 at 1 mol/L
95
What pH range is stable for most viruses
Between pH values of 5.0 and 9.0
96
Which viruses are resistant to acidic conditions
Enteroviruses
97
What is the effect of ultraviolet x-ray and high-energy particles on viruses
Inactivation of infectivity
98
How can enveloped viruses be distinguished from nonenveloped ones
By ether susceptibility testing
99
What do nonionic detergents like Nonidet P40 and Triton X-100 do to viruses
Solubilize lipid constituents of viral membranes
100
What do anionic detergents like SDS do to viruses
Solubilize envelopes and disrupt capsids into polypeptides
101
How does formaldehyde destroy viral infectivity
By reacting with nucleic acid
102
Which genomes are more susceptible to formaldehyde inactivation
Single-stranded genomes
103
What is photodynamic inactivation in viruses
Binding of vital dyes like toluidine blue neutral red or proflavine to nucleic acid followed by exposure to visible light
104
Do antibacterial antibiotics affect viruses
No effect on viruses
105
Which agents require larger concentrations to destroy viruses than bacteria
Chlorine especially in the presence of extraneous proteins
106
What are common methods for inactivating viruses
Steam under pressure dry heat ethylene oxide and γ-irradiation
107
What is used for sterilizing heat-resistant materials
Steam under pressure
108
What is used for materials that cannot withstand moisture
Dry heat
109
What is the gas sterilization method effective against a wide range of microorganisms
Ethylene oxide
110
What is used for penetrating packaging without heat
γ-irradiation
111
What surface disinfectants are commonly used
Hypochlorite glutaraldehyde formaldehyde and peracetic acid
112
What is the effect of hypochlorite on viruses
Broad-spectrum virucidal activity
113
What is the effect of glutaraldehyde on viruses
Cross-linking viral proteins
114
What is the effect of formaldehyde on viruses
Reacting with nucleic acids and proteins
115
What is the effect of peracetic acid on viruses
Oxidizing agent
116
What skin disinfectants are used
Chlorhexidine 70% ethanol and iodophores
117
What is the effect of chlorhexidine on viruses
Disrupting viral envelopes
118
What is the effect of 70% ethanol on viruses
Denaturing viral proteins
119
What is the effect of iodophores on viruses
Oxidizing viral components
120
What methods are used for inactivating viruses in vaccine production
Formaldehyde β-propiolactone psoralen + UV and detergents
121
What is the effect of formaldehyde in vaccine production
Cross-linking proteins and nucleic acids
122
What is the effect of β-propiolactone in vaccine production
Alkylating nucleic acids and proteins
123
What is the effect of psoralen + UV in vaccine production
Photochemical inactivation
124
What is the effect of detergents in vaccine production
Disrupting viral envelopes
125
What is the first step in viral replication
Attachment
126
What is attachment in viral replication
Interaction with a specific receptor
127
What type of receptor does picornavirus bind to
Protein sequence
128
What type of receptor do orthomyxovirus and paramyxovirus bind to
Oligosaccharides
129
What receptor does HIV bind to
CD4
130
What co-receptors are needed for HIV attachment
CXCR4 and CCR5
131
What receptor does influenza virus bind to
Sialic acid
132
What receptor does rabies virus bind to
Acetylcholine
133
What receptor does rhinovirus bind to
ICAM-1
134
What receptors does Epstein-Barr virus bind to
Complement receptor C3d and CD21
135
What receptors does poliovirus bind to
Ig superfamily molecules
136
What is the second step in viral replication
Penetration or engulfment
137
What methods are used for viral penetration
Endocytosis direct penetration and membrane fusion
138
What is the third step in viral replication
Uncoating
139
What is uncoating in viral replication
Separation of viral nucleic acid from capsid
140
Where do RNA viruses typically release their genome
Cytoplasm
141
Where do DNA viruses typically release their genome
Nucleus
142
What is the next step after uncoating in viral replication
Expression and synthesis of viral components
143
What is necessary for successful expression of viral genomes
mRNA transcription
144
What is unique about negative strand RNA viruses
Supplying their own RNA polymerase
145
What is the final step in viral replication
Morphogenesis and release
146
What occurs during morphogenesis
Assembly of viral components
147
How do nonenveloped viruses release from cells
Cell lysis
148
How do enveloped viruses release from cells
Budding
149
What is the primary location of replication for DNA viruses
Nucleus
150
What is the primary location of replication for RNA viruses
Cytoplasm
151
What is the role of nonstructural proteins in viral replication
Assisting replication and transcription
152
What is the role of structural proteins in viral replication
Forming capsid and envelope
153
What is the final step in viral assembly
Nucleocapsid formation
154
What is the purpose of viral glycoproteins in the envelope
Facilitating attachment and fusion
155
What type of mRNA is produced by dsDNA viruses
+mRNA
156
What are examples of dsDNA viruses
Herpesvirus and adenovirus
157
What intermediate is present in ssDNA viruses
dsDNA
158
What type of mRNA is produced by ssDNA viruses
+mRNA
159
What is an example of ssDNA viruses
Parvoviruses
160
What type of mRNA is produced by dsRNA viruses
+mRNA
161
What is an example of dsRNA viruses
Reoviruses
162
What enzyme is contained in the virion of reoviruses
RNA polymerase
163
What type of mRNA is produced by ssRNA viruses
+mRNA
164
What are examples of ssRNA viruses
Picornaviruses togaviruses and flaviviruses
165
What property does viral nucleic acid of ssRNA viruses have
It's infectious and serves as mRNA
166
What type of mRNA is produced by -ssRNA viruses
+mRNA
167
What are examples of -ssRNA viruses
Rhabdoviruses paramyxoviruses and orthomyxoviruses
168
What enzyme is contained in the virion of -ssRNA viruses
RNA polymerase
169
What type of mRNA is produced by +ssRNA retroviruses
+mRNA
170
What intermediate is present in +ssRNA retroviruses
-DNA and dsDNA
171
What enzyme is contained in the virion of retroviruses
Reverse transcriptase
172
What is the direct transmission of viruses from person to person by contact exemplified by
Coronavirus
173
What are examples of viral transmission via droplet or aerosol infection
Influenza measles and smallpox
174
What are examples of viral transmission via sexual contact
Papillomavirus hepatitis B herpes simplex type 2 and HIV
175
What are examples of viral transmission via hand-mouth hand-eye or mouth-mouth contact
Herpes simplex rhinovirus and Epstein-Barr virus
176
What are examples of viral transmission via exchange of contaminated blood
Hepatitis B and HIV
177
What are examples of viral transmission via the fecal-oral route
Enteroviruses rotaviruses and infectious hepatitis A
178
What are examples of viral transmission via fomites
Norwalk virus and rhinovirus
179
What are examples of transmission from animal to animal with humans as an accidental host
Rabies arenaviruses and hantaviruses
180
What are examples of transmission by means of an arthropod vector
Togaviruses flaviviruses and bunyaviruses
181
What human-arthropod cycle is recognized among arthropod-borne viruses
Lower vertebrate–arthropod cycle with tangential infection of humans
182
What are the factors contributing to disease emergence
Environmental changes human behavioral socioeconomic demographic phenomena travel commerce food production healthcare microbial adaptation and public health measures
183
What type of mRNA is produced by dsDNA viruses
+mRNA
184
What are examples of dsDNA viruses
Herpesvirus and adenovirus
185
What intermediate is present in ssDNA viruses
dsDNA
186
What type of mRNA is produced by ssDNA viruses
+mRNA
187
What is an example of ssDNA viruses
Parvoviruses
188
What type of mRNA is produced by dsRNA viruses
+mRNA
189
What is an example of dsRNA viruses
Reoviruses
190
What enzyme is contained in the virion of reoviruses
RNA polymerase
191
What type of mRNA is produced by ssRNA viruses
+mRNA
192
What are examples of ssRNA viruses
Picornaviruses togaviruses and flaviviruses
193
What property does viral nucleic acid of ssRNA viruses have
It's infectious and serves as mRNA
194
What type of mRNA is produced by -ssRNA viruses
+mRNA
195
What are examples of -ssRNA viruses
Rhabdoviruses paramyxoviruses and orthomyxoviruses
196
What enzyme is contained in the virion of -ssRNA viruses
RNA polymerase
197
What type of mRNA is produced by +ssRNA retroviruses
+mRNA
198
What intermediate is present in +ssRNA retroviruses
-DNA and dsDNA
199
What enzyme is contained in the virion of retroviruses
Reverse transcriptase
200
What is direct viral transmission from person to person exemplified by
Coronavirus
201
What are examples of viral transmission via droplet or aerosol
Influenza measles and smallpox
202
What are examples of viral transmission via sexual contact
Papillomavirus hepatitis B herpes simplex type 2 and HIV
203
What are examples of viral transmission via hand-mouth contact
Herpes simplex rhinovirus and Epstein-Barr virus
204
What are examples of viral transmission via contaminated blood
Hepatitis B and HIV
205
What are examples of viral transmission via the fecal-oral route
Enteroviruses rotaviruses and infectious hepatitis A
206
What are examples of viral transmission via fomites
Norwalk virus and rhinovirus
207
What are examples of transmission from animal to human
Rabies arenaviruses and hantaviruses
208
What are examples of transmission via arthropod vector
Togaviruses flaviviruses and bunyaviruses
209
What cycle is recognized among arthropod-borne viruses
Human-arthropod cycle
210
What are factors contributing to disease emergence
Environmental changes human behavior socioeconomic factors travel food healthcare microbial adaptation public health
