Questions on Virus – Characteristics, Structure, Classification & Origin
Multiple-Choice Questions: Virus – Characteristics, Structure, Classification & Origin
Characteristics and Structure
1. What is the basic structural component of all viruses?
A) Cell wall
B) Ribosome
C) Capsid
D) Cytoplasm
E) Chloroplast
2. Viruses are considered non-living because:
A) They cannot be seen with a microscope
B) They are made of only RNA
C) They do not contain nucleic acids
D) They do not carry out metabolism or reproduce independently
E) They have too many cells
3. The genetic material of a virus can be:
A) Only DNA
B) Only RNA
C) DNA or RNA, but never both
D) Both DNA and RNA simultaneously in all viruses
E) Neither DNA nor RNA
4. The protein coat surrounding a viral genome is called:
A) Envelope
B) Capsid
C) Nucleoid
D) Membrane
E) Capsule
5. What is a viral envelope?
A) The nuclear membrane of the host cell
B) The capsid of the virus
C) A lipid membrane derived from the host cell
D) A bacterial cell wall
E) A type of DNA
Classification and Types
6. Viruses are classified mainly based on:
A) Color
B) Size
C) Shape and genetic material
D) Habitat
E) Host metabolism
7. A bacteriophage is a virus that infects:
A) Fungi
B) Plants
C) Protozoa
D) Bacteria
E) Algae
8. The virus responsible for AIDS is:
A) HCV
B) HPV
C) HIV
D) HSV
E) H1N1
9. Which of the following is a DNA virus?
A) HIV
B) Influenza virus
C) Herpes simplex virus
D) Measles virus
E) Coronavirus
10. Viruses with RNA as genetic material include:
A) Adenoviruses
B) Herpesviruses
C) Retroviruses
D) Papillomaviruses
E) Poxviruses
Viral Replication and Life Cycle
11. Which viral replication cycle causes the immediate destruction of the host cell?
A) Lysogenic
B) Binary fission
C) Lytic
D) Budding
E) Transformation
12. The lysogenic cycle is characterized by:
A) Immediate host cell death
B) Viral DNA integrating into the host genome
C) RNA replication in cytoplasm
D) Production of viral toxins
E) Host cell immunity
13. Retroviruses convert their RNA into DNA using:
A) Ribosomes
B) RNA polymerase
C) DNA helicase
D) Reverse transcriptase
E) Ligase
14. What happens during viral budding?
A) The host cell dies instantly
B) The virus destroys the host nucleus
C) The virus exits the host cell without killing it
D) The host cell merges with another
E) The virus loses its envelope
15. Viral DNA integrated into the host DNA is called:
A) Capsid
B) Prophage
C) Virion
D) Phagosome
E) Pathogen
Origin and Evolution
16. One theory suggests viruses may have originated from:
A) Bacteria only
B) Pre-cellular life
C) Extraterrestrial sources only
D) Fossilized eukaryotes
E) Protein crystals
17. The progressive hypothesis suggests that viruses originated from:
A) Free-living prokaryotes
B) Host cell DNA or RNA fragments
C) Fossils
D) Plant chloroplasts
E) Archaea
18. According to the regressive hypothesis, viruses may have evolved from:
A) Symbiotic bacteria that lost functions
B) Fungi
C) Ribosomes
D) Plant cells
E) Mitochondria
19. Which viral structure is responsible for recognizing host cells?
A) DNA
B) Capsid
C) Envelope
D) Glycoproteins
E) Ribosomes
20. Which of the following is true about viruses?
A) All viruses have envelopes
B) Viruses have mitochondria
C) Viruses are unicellular
D) Viruses reproduce only inside living cells
E) Viruses perform photosynthesis
Virus Examples and Impacts
21. The virus that causes COVID-19 is classified as:
A) Retrovirus
B) DNA virus
C) Coronavirus
D) Poxvirus
E) Flavivirus
22. Which of the following viral infections is preventable by vaccine?
A) HIV
B) Influenza
C) Ebola
D) Common cold
E) Rabies
23. Which of the following viruses affects plants?
A) Adenovirus
B) Tobacco mosaic virus
C) Norovirus
D) Cytomegalovirus
E) Rabies virus
24. Viruses can be crystallized because:
A) They are not alive
B) They contain only RNA
C) They are made of water
D) They are part of fungi
E) They have chloroplasts
25. The complete infectious form of a virus outside a host cell is called a:
A) Prion
B) Plasmid
C) Virion
D) Capsid
E) Nucleoid
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Answer Key with Explanations
1. C – The capsid is the protein coat of a virus.
2. D – Viruses are not cells and do not carry out metabolic functions or reproduce independently.
3. C – A virus has either DNA or RNA, but not both.
4. B – The capsid encloses the genetic material.
5. C – Some viruses have a lipid envelope from the host membrane.
6. C – Classification is based on shape and type of genetic material.
7. D – Bacteriophages infect bacteria.
8. C – HIV (Human Immunodeficiency Virus) causes AIDS.
9. C – Herpes simplex virus is a DNA virus.
10. C – Retroviruses (like HIV) have RNA as their genetic material.
11. C – The lytic cycle destroys the host cell.
12. B – The lysogenic cycle involves integration into the host genome.
13. D – Reverse transcriptase is used by retroviruses to convert RNA into DNA.
14. C – Budding allows viruses to exit the host without killing it.
15. B – Prophage is viral DNA integrated into host DNA.
16. B – Viruses may have originated before cells (pre-cellular life).
17. B – The progressive hypothesis proposes viral origin from mobile genetic elements.
18. A – The regressive hypothesis suggests viruses evolved from more complex organisms.
19. D – Glycoproteins on the envelope bind to receptors on host cells.
20. D – Viruses require a host cell to reproduce.
21. C – COVID-19 is caused by a coronavirus (SARS-CoV-2).
22. B – Influenza can be prevented with vaccines.
23. B – Tobacco mosaic virus infects plants.
24. A – Viruses can be crystallized because they are acellular and non-living outside hosts.
25. C – A virion is a complete virus particle capable of infection.
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