#1
What is the main purpose of viral plaque assays?
To observe the color change in viral cultures
To measure the concentration of viruses in a sample
To identify the type of virus
To observe the size of the virus
#2
What does a plaque represent in a viral plaque assay?
A single infected cell
A cluster of viruses
A clear zone of lysed cells
A contaminated area
#3
What is the principle behind the formation of plaques in a monolayer of cells?
Cellular respiration
Photosynthesis
Viral lytic cycle
Mitosis
#4
Which statement best describes a 'pfu' in the context of viral quantification?
Particle forming unit, indicating the total number of viral particles
Plaque forming unit, indicating the number of virus particles capable of forming plaques
Protein forming unit, related to the amount of viral protein produced
Particle filtration unit, a measure of viral filterability
#5
Why is it important to achieve a uniform monolayer of host cells in a plaque assay?
To ensure equal exposure of all cells to the virus
To make the assay process faster
To reduce the amount of virus needed
To prevent the need for serial dilutions
#6
Which of the following is NOT a component of the medium used in plaque assays?
Agar
Antibiotics
Viruses
Nutrients
#7
How is the titer of a viral sample calculated using a plaque assay?
By counting the number of cells in the sample
By measuring the diameter of plaques
By counting the number of plaques and adjusting for dilution factors
By the intensity of color change in the medium
#8
Which type of cells are commonly used for viral plaque assays?
Bacterial cells
Plant cells
Animal cells
Fungal cells
#9
Why are overlays used in viral plaque assays?
To prevent evaporation of the medium
To restrict the spread of viruses to a two-dimensional plane
To increase the rate of viral infection
To enhance the visibility of plaques
#10
What role does the incubation period play in viral plaque assays?
It determines the color of the plaques
It allows sufficient time for viral replication and plaque formation
It decreases the virulence of the virus
It increases the size of the host cells
#11
In the context of viral plaque assays, what is the purpose of staining the cell layer?
To identify the type of cells in the monolayer
To increase the contrast between plaques and the uninfected cell layer
To measure the concentration of the virus directly
To promote the growth of the virus
#12
What is the significance of using a serial dilution in viral plaque assays?
To increase the concentration of the virus
To decrease the sensitivity of the assay
To obtain a countable number of plaques
To enhance the color of the plaques
#13
How does the presence of a viral envelope affect plaque assays?
Enveloped viruses do not form plaques
Enveloped viruses form larger plaques
Enveloped viruses require special additives to form plaques
There is no significant effect
#14
Which factor does NOT influence the size and clarity of plaques in viral plaque assays?
The type of overlay medium used
The temperature at which the assay is incubated
The color of the medium
The virulence of the virus
#15
What impact does the multiplicity of infection (MOI) have on plaque assay results?
Higher MOI leads to smaller plaques due to limited host cell availability
Higher MOI increases the speed of plaque formation
Lower MOI results in the formation of more plaques
MOI has no significant impact on the results
#16
How do antiviral compounds affect viral plaque assays?
They increase the size of the plaques
They prevent plaque formation entirely
They can reduce the number or size of plaques, indicating antiviral activity
They change the color of the plaques to indicate effectiveness
#17
Which factor is NOT typically varied to optimize plaque assay conditions?
The type of lighting used during incubation
The concentration of agar in the overlay medium
The incubation temperature
The volume of virus inoculum added