Free Viruses MCQs with Answers
247 Viruses MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Viruses are acellular infectious particles made of genetic material enclosed by a protein capsid, sometimes with a lipid envelope. Their replication depends on a host cell and may follow lytic or lysogenic cycles, so viral structure and reproduction differ fundamentally from those of cellular organisms such as bacteria.
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- A. It can be cured with a course of antibiotics
- B. It survives for weeks on dry surfaces
- C. It is commonly spread by mosquito bites
- D. It destroys helper T cells and progressively weakens immunity
Explanation: HIV replicates inside helper T lymphocytes and destroys them, so immunity collapses and opportunistic infections follow.
Correct answer: It destroys helper T cells and progressively weakens immunity- A. They always infect animal cells only
- B. Their RNA acts directly as mRNA
- C. They lack protein coats
- D. They use reverse transcriptase to make DNA from RNA
Explanation: A retrovirus reverses the usual flow of information by copying its RNA genome into DNA, which integrase then inserts into the host…
Correct answer: They use reverse transcriptase to make DNA from RNA- A. Paramyxovirus
- B. Rhinovirus
- C. Arbovirus
- D. Rhabdovirus
Explanation: Rabies is caused by rabies virus, a member of the genus Lyssavirus in the family Rhabdoviridae, whose virions are characteristically…
Correct answer: Rhabdovirus- A. DNA
- B. RNA
- C. Protein
- D. Both A & B
Explanation: Viruses have genomes made of nucleic acid, and different viruses may contain either DNA or RNA, although an individual virus normally…
Correct answer: Both A & B- A. Circulate
- B. Move
- C. Reproduce
- D. Are crystalline
Explanation: Viruses resemble living organisms because they can reproduce inside a suitable host cell using the host's machinery.
Correct answer: Reproduce- A. Poliomyelitis
- B. Common cold
- C. Yellow fever
- D. Diphtheria
- E. Encephalitis
Explanation: Diphtheria is caused by the bacterium Corynebacterium diphtheriae, not by a virus.
Correct answer: Diphtheria- A. Cellular
- B. Prokaryotes
- C. Non-cellular
- D. Eukaryotes
Explanation: Viruses are non-cellular because they lack cytoplasm, ribosomes and independent cellular metabolism.
Correct answer: Non-cellular- A. RNA
- B. Protein
- C. DNA
- D. None of these
Explanation: Nearly all known bacteriophages have DNA as their genetic material, although a small number of phages possess RNA genomes.
Correct answer: DNA- A. Cowpox
- B. Mumps
- C. Tetanus
- D. Small pox
Explanation: Tetanus is caused by the bacterium Clostridium tetani, whereas cowpox, mumps, and smallpox are viral diseases.
Correct answer: Tetanus- A. Measles
- B. Polio
- C. Small pox
- D. Hepatitis
Explanation: Smallpox was eradicated worldwide through an effective coordinated vaccination programme, and the World Health Organization declared…
Correct answer: Small pox- A. Measles
- B. Cancer
- C. Diabetes
- D. Heart attack
Explanation: Measles is caused by a virus and can be effectively prevented through vaccination, which prepares immune memory before infection occurs.
Correct answer: Measles- A. virion
- B. mycoplasma
- C. viroids
- D. prions
Explanation: Viroids are the smallest known infectious agents of plants and consist only of short, circular strands of RNA without a protein coat.
Correct answer: viroids- A. bacteria
- B. fungi
- C. virus
- D. none of these
Explanation: Bacteria cause many diseases that can be treated with antibiotics because antibiotics target bacterial structures or processes, such as…
Correct answer: bacteria- A. It is a non-cellular entity
- B. Obligate parasite
- C. Ultramicroscopic in size
- D. All of these
Explanation: Viruses are non-cellular particles made of genetic material surrounded by a protein coat, and they are usually ultramicroscopic.
Correct answer: All of these- A. Ligase
- B. Endonuclease
- C. Exonuclease
- D. Gyrase
Explanation: Restriction endonucleases protect bacteria by cutting invading viral DNA at specific internal recognition sequences, thereby disabling the…
Correct answer: Endonuclease- A. Bacteria
- B. Virus
- C. Cyanobacteria
- D. Plants
Explanation: Viruses are considered a link between living and non-living matter because they show living activity only inside host cells, while outside…
Correct answer: Virus- A. Rubella
- B. Common cold
- C. Influenza
- D. None of the above
Explanation: Rubella, the common cold and influenza can all spread through infectious respiratory droplets, so none of the listed diseases is excluded.
Correct answer: None of the above- A. Obligate parasite
- B. Autotrophs
- C. Heterotrophs
- D. Absorptive heterotrophs
Explanation: Viruses are obligate parasites because they lack the cellular machinery needed for independent metabolism and reproduction, so they must…
Correct answer: Obligate parasite- A. MERS
- B. SARS-CoV-2
- C. OC43
- D. HKUt
Explanation: SARS-CoV-2 is an emergent coronavirus that caused the COVID-19 pandemic and millions of deaths worldwide.
Correct answer: SARS-CoV-2- A. Rest period
- B. Incubation period
- C. Sleeping period
- D. Inclubation time
Explanation: The incubation period is the time between entry of a pathogen into the body and the appearance of disease symptoms.
Correct answer: Incubation period