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Week 3 Flashcards

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1
Q

How do viruses survive?

A
  • virions produced in the infected hosts must be transmitted to new hosts
  • viral genes maintained in cells as nucleic acids
  • (bacteria) viruses released from infected cells into the environment
  • (plants) viruses spread to adjacent cells
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2
Q

T/F. Viruses can modify the behavior of their hosts in order to increase the probability of transmission.

A

True. baculoviruses, rabies, iridovirus

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3
Q

Describe the classical route of viral infection.

A

Cell-free virions bind to host cells with receptor-ligand interactions, fuse into cytoplasm, and then replicate.
- released into environment

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4
Q

What are the two special junctions called that small viruses transmit through in the cell membrane for animal and plant cells?

A

animal: gap junctions
plant: plasmodesmata

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5
Q

Describe cell to cell transmission for viral infection.

A
  • actively infected cell can directly infect a second cell
  • no need to be released into environment
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6
Q

What is the disadvantage of the classical route vs. cell to cell transmission in viral infection?

A
  • virus is exposed
  • antibody has time to react
  • exposure to protein detergent (disrupts viral envelope)
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7
Q

When a virus is transmitted between hosts by organisms that feed on them these are called?

A

vectors

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8
Q

Why do many plant viruses need vectors?

A
  • cell walls pose as barriers
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9
Q

Transmission of invertebrate viruses in insects are transmitted primarily by:
A. other insects
B. vectors
C. occlusion bodies
D. cell-to-cell transmission

A

C. occlusion bodies

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10
Q

List some non-vector transmission paths (horizontal/vertical) in vertebrate viruses.

A
  • mucous membranes (flu)
  • respiratory tract (flu, measles)
  • skin lesions (herpes, rabies, HIV)
  • intestinal tract (rotavirus)
  • mother to baby via placenta (HIV)
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11
Q

Which inanimate vectors exist for transmission of vertebrate viruses?

A
  • needles
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12
Q

Which is the disease name and which is the name of the virus:
COVID-19
SARS-CoV-2

A

COVID-19: disease
SARS-CoV-2: virus

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13
Q

What are the 3 types of SARS-CoV-2 transmission?

A
  1. Contact: direct contact with infectious person (touching mouth, nose, or eyes)
  2. Droplet: exposure to respiratory droplets exhaled by infectious person
  3. Airborne: exposure to virus-containing respiratory droplets in air over distances and a certain amount of hours
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14
Q

List defense mechanisms in vertebrates against viral infection.

A
  • removal by mucociliary escalator
  • extreme pH of GI tract
  • surface fluids that contain antiviral substances (detergent)
  • phagocytosis
  • antibodies
  • vaccines
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15
Q

What factors allow permissive cells to infect animal and plant hosts?

A
  • appropriate receptors
  • host cell must have transcription factors and enzymes
  • certain phase of cell cycle (retroviruses = reverse transcriptase)
  • lack defenses against virus
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16
Q

Why do nonpermissive cells survive viral challenge?

A
  • viral replication does not occur
  • minimum number of virions to infect host not met
  • virus may be inactive and host is not compatible to activate it
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17
Q

List the 7 steps of viral replication. (Animals, Eat, To, Take, Good, Ass, Exits)

A
  1. ATTACHMENT of virion to cell
  2. ENTRY into cell
  3. TRANSCRIPTION of virus genes into mRNA
  4. TRANSLATION of virus mRNA into viral proteins
  5. GENOME REPLICATION
  6. ASSEMBLY of proteins and genomes into virions
  7. EXIT of virions from cell
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18
Q

Which of the 7 viral replication steps can be skipped?

A
  • Transcription
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19
Q

Receptors in animal cells are cell surface molecules made of:
A. chemokines
B. lipids and carbohydrates
C. peptidoglycan

A

B. lipids and carbohydrates

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20
Q

Which type of bonds will LEAST likely allow for virus attachment to a receptor?
A. hydrogen bonds
B. ionic bonds
C. van der waals forces
D. non-covalent bonds
E. covalent bonds

Study These Flashcards
A

E. covalent bonds

21
Q

What must occur in this picture for the virus binding to be efficient?

Study These Flashcards
A
  • the viral protein must undergo a conformational change for the coreceptor to bind
22
Q

Why are neutralizing antibodies important against virus-cell receptor interaction?

Study These Flashcards
A
  • antibodies bind to the virus so there can be no viral attachment to receptors on host cell
  • can be a signal to immune cells to perform phagocytosis
23
Q

An epitope is:

Study These Flashcards
A

an antigenic determinant recognized by the immune system (T-cells or B-cells)

24
Q

Describe the difference between monoclonal and polyclonal.

Study These Flashcards
A

Monoclonal: single epitope recognized
- highly successful in blocking viral attachment

Polyclonal: multiple epitopes recognized
- all antibodies pulled together
- least likely to block viral attachment

25
Describe the type of virus attachment site.
Naked virus attachment site: within depression, canyons - too narrow for antibodies to access (poliovirus)
26
During haemagglutination assay (HA), red blood cells agglutinate because A. The cells are connected via anti viral antibodies B. red blood cells are connected via haemagglutinins on the surface of viral envelope C. viruses bind to haemagglutinins on the surface of red blood cells and cause cell to agglutinate D. haemagglutinins on red blood cell surface bind to each other and cause cell to agglutinate
B. red blood cells are connected via haemagglutinins on the surface of viral envelope
27
If a monoclonal antibody against haemagglutinin is added to haemagglutination assay, what will happen?
A. it will enhance the aggregation of RBCs B. it will reduce or even block aggregation of RBCs C. it will have no effect on the aggregation of RBCs
28
Describe the entry of this animal virus into the host cell. Is it a naked virus or enveloped virus?
Fuses directly with the plasma membrane through a pore - naked virus - endocytosis
29
Describe the entry of this animal virus into the host cell.
Enveloped viruses require an acid pH fusion from the endosome to cross membrane
30
Where does the complete or partial removal of the capsid take place?
- cell surface, capsid remains on exterior of the cell - within the cytoplasm - at nuclear pore - within the nucleus
31
Is viral entry into the cell always followed by virus replication?
No, there can be enzymes that inactivate infectivity or the virus genome may initiate a latent infection
32
Most RNA viruses replicate in (_____). A. cytoplasm B. nucleus C. nuclear pore
A. cytoplasm
33
On the phage and cell side, how does binding occur?
Phage: virus attachment sites are on virion structures like tail fibres Cell: molecules are on surface of the host cell wall
34
For bacteriophages, which of the following enter the enter into the cell: - virus genome - capsid - associated appendages - all of the above
- virus genome ONLY
35
The virus genome is divided into how many classes and types of viruses?
- 7 classes - RNA, DNA, and reverse transcribing viruses
36
Which direction is RNA or DNA synthesized and coded from?
Read: 3'-5' Coded: 5'-3'
37
mRNA is the same as.... A. (-)RNA B. (+)RNA
B. (+)RNA
38
Is (-)RNA known as the same sequence as mRNA or the complement sequence?
- complement sequence
39
(+)RNA and (+)DNA have the (______) sequence as the mRNA A. same B. complement
A. same - DNA replaces Thymine (T) with Uracil (U)
40
(-)RNA and (-)DNA have the (______) sequence as the mRNA A. same B. complement
B. complement
41
Which genome class can function as mRNA?
Class IV
42
How many hosts do ambisense viruses have? A. one host B. two hosts
B. two hosts
43
Which of the following does NOT function as a DNA primer during viral genome replication? A. DNA B. RNA C. Lipid D. Protein
C. Lipid
44
T/F. Protein primers reside on a serine or tyrosine and are not removed once their role is performed.
True
45
In ssRNA, how does replication occur?
- replicated by synthesis of complementary strands - complementary strands are used as templates for new copies of the genome
46
Which genome classes use an intermediate for genome replication?
- class VI - class VII (reverse transcriptase)
47
If a segment of a Group VI virus genome is: 5' AUGGCC 3', then the next intermediate product it makes during genome replication is? A. 3' UACCGG 5’ B. 3' TACCGG 5’ C. 5' UACCGG 3’ D. 5' TACCGG 3’
B. 3' TACCGG 5’
48
If a segment of a –ssRNA virus genome is: 5' AUGGCCACC 3’, the peptide sequence coded by this segment of genome is:
3' UACCGGUGG 5' - change mRNA to DNA code from 5' to 3' Gly- Gly-His

Virology (5 decks)

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