Positive Staining of Viruses MCQs Mock Test (30 MCQs)

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Learn about positive staining methods for virus detection in clinical and research settings. This comprehensive guide covers:

✓ Principles of Positive Staining (dye-binding mechanisms)
✓ Key Techniques:

Immunohistochemistry (IHC) – Antibody-based detection
Immunofluorescence (IF) – Fluorescent tagging of viral antigens
Hematoxylin & Eosin (H&E) – Histopathological identification of viral inclusions
Giemsa Staining – Viral cytopathic effects in cell cultures
Electron Microscopy (EM) Stains – Heavy metal contrasting (e.g., uranyl acetate)

✓ Diagnostic Applications:

Herpesviruses (Cowdry type A inclusions)
Rabies (Negri bodies in neurons)
Cytomegalovirus (CMV) (Owl’s eye inclusions)
Respiratory viruses (RSV, Influenza)

✓ Comparison with Negative Staining (for EM visualization)
✓ Troubleshooting Common Staining Issues

Essential for virologists, pathologists, and clinical lab professionals working in infectious disease diagnostics.

Test your knowledge with 30+ MCQs on positive viral staining methods, covering:
◼️ Identification of viral inclusion bodies
◼️ Selection of appropriate staining techniques (IHC vs. IF vs. H&E)
◼️ Interpretation of stained samples
◼️ Common pitfalls and artifacts

Perfect for medical students, virology researchers, and lab technicians preparing for certification exams.

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Microbiology Department

Positive staining of Viruses MCQs Mock Test

Perfect for medical students, virology researchers, and lab technicians preparing for certification exams.

Read Full Article: Positive staining of Viruses 50 FAQ and 30 MCQs

1 / 30

Category: Clinical Laboratory

What is a limitation of positive staining?

It cannot visualize viral structures

It is faster than negative staining

It does not require heavy metals

It is sensitive to CO₂ and light

2 / 30

Category: Clinical Laboratory

Which viral structure is NOT typically visible with positive staining?

Spikes

Envelope

Viral RNA sequence

Capsid

3 / 30

Category: Clinical Laboratory

How does positive staining help in vaccine development?

By killing viruses

By sequencing viral DNA

By making viruses invisible

By providing structural details for antigen design

4 / 30

Category: Clinical Laboratory

What is a major advantage of positive staining?

It does not require an electron microscope

It works only for bacteria

It provides functional data on viral replication

It is simple and provides high-contrast images

5 / 30

Category: Clinical Laboratory

How long should a grid be incubated in uranyl acetate for optimal staining?

1 second

30 seconds to 15 minutes

1 hour

24 hours

6 / 30

Category: Clinical Laboratory

What is the first step in positive staining?

Staining with uranyl acetate

Fixation with glutaraldehyde

Immediate TEM observation

Sample purification and concentration

7 / 30

Category: Clinical Laboratory

Can positive staining be combined with immunogold labeling?

No, they are incompatible

Yes, for targeted protein visualization

Only for bacteria

Only in light microscopy

8 / 30

Category: Clinical Laboratory

How should uranyl acetate waste be disposed of?

In a regular trash bin

In designated radioactive/chemical waste containers

By burning it

By flushing down the sink

9 / 30

Category: Clinical Laboratory

What magnification is typically used for virus observation?

10,000x–100,000x

1,000,000x

100x–1,000x

1,000x–5,000x

10 / 30

Category: Clinical Laboratory

What is the role of heavy metal salts in positive staining?

They increase electron density for better contrast

They dissolve viral proteins

They make viruses invisible under TEM

They prevent staining artifacts

11 / 30

Category: Clinical Laboratory

What future improvement is expected in positive staining?

Replacement with Gram staining

Elimination of TEM

New stains and reduced artifacts

No further advancements

12 / 30

Category: Clinical Laboratory

Which staining method combines uranyl acetate, glutaraldehyde, and PVA?

Immunogold staining

Gram staining

Tokuyasu staining procedure (TSP)

Negative staining

13 / 30

Category: Clinical Laboratory

How is excess stain removed from the grid after staining?

By using a strong acid

By washing with ultra-purified water

By heating the grid

By freezing the sample

14 / 30

Category: Clinical Laboratory

Which stain is best for visualizing viral lipid envelopes?

Uranyl acetate

Lead citrate

Methylene blue

Osmium tetroxide

15 / 30

Category: Clinical Laboratory

What does a dark region in a positively stained TEM image represent?

Electron-dense viral structures

Background

Unstained area

Artifacts

16 / 30

Category: Clinical Laboratory

What is the purpose of washing grids after staining?

To remove excess stain and prevent artifacts

To make the grid sterile

To dissolve the virus

To increase staining intensity

17 / 30

Category: Clinical Laboratory

Why must lead citrate staining be performed in a CO₂-free environment?

CO₂ enhances staining

CO₂ reacts with lead citrate, causing precipitates

CO₂ makes viruses invisible

CO₂ improves resolution

18 / 30

Category: Clinical Laboratory

What is the correct concentration of uranyl acetate typically used?

10%

0.1%

19 / 30

Category: Clinical Laboratory

Which technique preserves native virus structure better than positive staining?

Gram staining

Light microscopy

Cryo-EM

PCR

20 / 30

Category: Clinical Laboratory

Why is uranyl acetate hazardous?

It is edible

It is harmless

It improves eyesight

It is radioactive and toxic

21 / 30

Category: Clinical Laboratory

Why is fixation necessary before staining?

To preserve viral structure

To make the virus fluorescent

To dissolve the virus

To reduce staining time

22 / 30

Category: Clinical Laboratory

Which virus has been studied using positive staining?

Saccharomyces cerevisiae

HIV-1

Escherichia coli

None of the above

23 / 30

Category: Clinical Laboratory

Which factor can cause staining artifacts?

Proper washing

Excess stain or contamination

Air-drying grids slowly

Using fresh uranyl acetate

24 / 30

Category: Clinical Laboratory

Which microscope is used to observe positively stained viruses?

Light microscope

Transmission Electron Microscope (TEM)

Scanning Electron Microscope (SEM)

Fluorescence microscope

25 / 30

Category: Clinical Laboratory

Why is uranyl acetate commonly used in positive staining?

It binds to proteins and nucleic acids✔

It binds to lipids only

It dissolves viral envelopes

It fluoresces under light

26 / 30

Category: Clinical Laboratory

How should grids be dried before TEM observation?

Heating at 100°C

Freezing in liquid nitrogen

Using a hairdryer

Air-drying or blotting with filter paper

27 / 30

Category: Clinical Laboratory

Which of the following is NOT a common stain used in positive staining?

Methylene blue

Lead citrate

Osmium tetroxide

Uranyl acetate

28 / 30

Category: Clinical Laboratory

What precaution is necessary when using osmium tetroxide?

Use in an open room

Work without gloves

No precautions needed

Use in a fume hood

29 / 30

Category: Clinical Laboratory

How does positive staining differ from negative staining?

Positive staining makes viruses appear dark on a light background

Both techniques produce the same results

Positive staining makes viruses appear light on a dark background

Negative staining is not used in virology

30 / 30

Category: Clinical Laboratory

What is the primary purpose of positive staining in electron microscopy?

To make the background dark

To reduce electron density

To enhance the contrast of virus particles

To dissolve viral structures

Your score is

The average score is 75%

Read Full Article: Positive staining of Viruses 50 FAQ and 30 MCQs

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