🧠 Practice MCQs – Viruses (MDCAT Biology)

🔹 A. Recall-Based MCQs (Factual/Direct)

Which scientist first crystallized the Tobacco Mosaic Virus?
A) Ivanovsky
B) Stanley
C) Twort
D) Beijerinck
➤ Answer: B) Stanley
What type of genetic material is found in viruses?
A) Only DNA
B) Only RNA
C) DNA and RNA
D) Either DNA or RNA
➤ Answer: D) Either DNA or RNA
Who coined the term “virus” as a “contagium vivum fluidum”?
A) Felix d'Herelle
B) Beijerinck
C) Stanley
D) Ivanovsky
➤ Answer: B) Beijerinck
What is the protein coat surrounding viral genetic material called?
A) Matrix
B) Envelope
C) Capsid
D) Plasmid
➤ Answer: C) Capsid
Which virus was the first to be discovered?
A) HIV
B) Influenza
C) TMV
D) Adenovirus
➤ Answer: C) TMV

🔍 B. Conceptual-Based MCQs (Understanding/Explanation)

Why are viruses considered non-living outside the host cell?
A) They are too small
B) They do not have cytoplasm
C) They cannot perform metabolism or reproduction
D) They mutate quickly
➤ Answer: C) They cannot perform metabolism or reproduction
Which feature makes viruses acellular?
A) They have no genetic material
B) They have no ribosomes or enzymes of their own
C) They undergo binary fission
D) They can respire only in bacteria
➤ Answer: B) They have no ribosomes or enzymes of their own
Why do RNA viruses mutate more frequently than DNA viruses?
A) They have more genes
B) RNA is more stable
C) RNA lacks proofreading enzymes
D) They infect animals more often
➤ Answer: C) RNA lacks proofreading enzymes
Which feature of viruses supports their classification as non-living?
A) Presence of capsid
B) Formation of inclusion bodies
C) Ability to be crystallized
D) Presence of RNA
➤ Answer: C) Ability to be crystallized
What does it mean that viruses are "host-specific"?
A) They infect every species they contact
B) They only infect plant cells
C) They require a host with a matching receptor
D) They reproduce only once
➤ Answer: C) They require a host with a matching receptor

🧠 C. Analytical-Based MCQs (Application & Reasoning)

A virus infects liver cells but not blood cells. What does this suggest about the virus?
A) It is temperature-sensitive
B) It lacks RNA
C) It is host-specific at the cellular level
D) It has a double protein coat
➤ Answer: C) It is host-specific at the cellular level
Which of the following situations best demonstrates the lytic cycle of a virus?
A) Virus inserts genes into host and stays dormant for years
B) Virus kills the host cell soon after replication
C) Host cell survives with viral DNA integrated in its genome
D) Virus mutates and avoids host immune response
➤ Answer: B) Virus kills the host cell soon after replication
A biologist finds a particle with no cytoplasm, no metabolism, but it contains RNA and a protein coat. What is the most probable identification?
A) Protozoa
B) Fungus spore
C) Virus
D) Prion
➤ Answer: C) Virus
Why can heat and alcohol be used to deactivate many viruses?
A) They denature host enzymes
B) They dissolve lipid envelopes or protein coats
C) They increase virus mutation
D) They replicate viral DNA
➤ Answer: B) They dissolve lipid envelopes or protein coats
A virus lacking a lipid envelope would most likely:
A) Be more easily destroyed by detergents
B) Infect fewer types of cells
C) Be more resistant to harsh environments
D) Be unable to mutate
➤ Answer: C) Be more resistant to harsh environments