Viruses

Viruses MDCAT MCQs with answers

48 past paper MCQs on Viruses, from the Acellular Life unit of MDCAT Biology. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

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1.What does the term bacteriophage refer to? (MDCAT 2022)

  1. a virus that infects bacteria
  2. a bacterium that infects a virus
  3. a virus which behaves as a bacterium
  4. a combination of a bacterium and a virion
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Correct answer: (a) a virus that infects bacteria

The name means bacteria-eater, and that is what these viruses do.

2.Which of the following viruses contains single stranded DNA? (MDCAT 2022)

  1. adenovirus
  2. herpes virus
  3. parvovirus
  4. poxvirus
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Correct answer: (c) parvovirus

The parvoviruses carry a single strand of DNA.

3.How many tail fibrils are attached to the end plate of a bacteriophage? (MDCAT 2022)

  1. 2
  2. 4
  3. 6
  4. 8
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Correct answer: (c) 6

Six fibrils spread from the end plate and hold the phage to the bacterial wall.

4.Which of the following viruses contains single stranded DNA? (MDCAT 2023)

  1. adenovirus
  2. herpes virus
  3. parvovirus
  4. poxvirus
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Correct answer: (c) parvovirus

The parvoviruses are the single stranded DNA viruses; the other three carry double stranded DNA.

5.An example of a virus having a polyhedral capsid with 252 capsomeres is: (MDCAT 2024)

  1. adenovirus
  2. tobacco mosaic virus
  3. influenza virus
  4. bacteriophage
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Correct answer: (a) adenovirus

The adenovirus capsid is an icosahedron built of 252 capsomeres.

6.The causative organism of measles is: (MDCAT 2024)

  1. poxvirus
  2. papovavirus
  3. picornavirus
  4. paramyxovirus
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Correct answer: (d) paramyxovirus

Measles is caused by the measles virus, a paramyxovirus.

7.In the life cycle of a bacteriophage, lysozyme is required in which step of the infection process? (MDCAT 2024)

  1. release of the new phages
  2. penetration
  3. replication
  4. adsorption
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Correct answer: (b) penetration

The enzyme digests a hole in the bacterial wall so the phage DNA can be injected.

8.Why are retroviruses placed in a separate class of RNA viruses? (UHS MDCAT 2025)

  1. They always infect animal cells only
  2. Their RNA acts directly as mRNA
  3. They lack protein coats
  4. They use reverse transcriptase to make DNA from RNA
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Correct answer: (d) They use reverse transcriptase to make DNA from RNA

A retrovirus carries reverse transcriptase, which copies its RNA into DNA for the host to integrate.

9.Which disease is caused by enveloped virus? (KMU MDCAT 2025)

  1. Leaf curl disease of cotton
  2. Flu
  3. Polio
  4. Hepatitis A
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Correct answer: (b) Flu

The influenza virus takes a lipid envelope from the host membrane as it leaves.

10.On the basis of morphological classification, influenza virus is an example of: (KMU MDCAT 2025)

  1. Helical capsid virus
  2. Polyhedral capsid virus
  3. Enveloped capsid virus
  4. Non-enveloped capsid virus
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Correct answer: (c) Enveloped capsid virus

Influenza is a helical virus wrapped in an envelope, so it is classed with the enveloped viruses.

11.Which of the following virus is having double stranded RNA in its core? (NUMS MDCAT 2025)

  1. Small pox
  2. Mild rash virus
  3. Diarrhea virus
  4. Rubella virus
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Correct answer: (c) Diarrhea virus

The rotavirus of infantile diarrhoea carries double stranded RNA.

12.Pore size of porcelain filter ranges between: (NUMS MDCAT 2025)

  1. 10 – 100 nm
  2. 100 – 1000 nm
  3. 10 – 10 μm
  4. 100 – 1000 μm
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Correct answer: (b) 100 – 1000 nm

A porcelain filter has pores of about 100 to 1000 nanometres, small enough to hold bacteria and let viruses through.

13.Reverse transcriptase converts: (NUMS MDCAT 2025)

  1. ds RNA to ss RNA
  2. ss RNA to ds RNA
  3. ss RNA to ds DNA
  4. ss DNA to ds DNA
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Correct answer: (c) ss RNA to ds DNA

Reverse transcriptase copies the single stranded RNA of a retrovirus into double stranded DNA.

14.Which group of viruses can cause diseases like influenza, measles and rabies? (SIBA MDCAT 2025)

  1. Plant viruses
  2. Animal viruses
  3. Fungal viruses
  4. Bacteriophages
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Correct answer: (b) Animal viruses

Influenza, measles and rabies viruses all multiply in animal cells.

15.Envelope in a virus is derived from (SZABMU MDCAT 2025)

  1. Host cell ribosomes
  2. Host cell membrane
  3. Viral capsid proteins
  4. Viral genome replication
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Correct answer: (b) Host cell membrane

An enveloped virus wraps itself in a piece of the host membrane as it buds out.

16.The shape of Adenovirus is: (SZABMU MDCAT 2025)

  1. Helical shape
  2. Tadpole shape
  3. Polyhedron shape
  4. Circular shape
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Correct answer: (c) Polyhedron shape

The adenovirus capsid is an icosahedron, that is a polyhedron.

17.Example of viruses having a polyhedral capsid that is with 252 capsomeres is: (UHS MDCAT 2024)

  1. Adenovirus
  2. Tobacco Mosaic Virus
  3. Influenza virus
  4. Bacteriophage
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Correct answer: (a) Adenovirus

The adenovirus capsid is an icosahedron built of 252 capsomeres.

18.In the life cycle of a bacteriophage, the lysozymes are required in which of the following steps of infection process? (UHS MDCAT 2024)

  1. Genome injection
  2. Penetration
  3. Replication
  4. Adsorption
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Correct answer: (b) Penetration

The tail lysozyme digests a hole in the bacterial wall so the genome can be driven in.

19.The genetic code of ________ is bound by a lipid membrane? (KMU MDCAT 2024)

  1. Enterovirus
  2. Flu virus
  3. Hepatitis A virus
  4. Polio virus
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Correct answer: (b) Flu virus

The influenza virus takes a lipid envelope from the host membrane; the picornaviruses are naked.

20.Viruses Can NOT _______. (KMU MDCAT 2024)

  1. Crystalize
  2. Excrete
  3. Infect bacteria
  4. Mutate
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Correct answer: (b) Excrete

A virus has no metabolism of its own, so it neither feeds nor excretes.

21.Which of the following is NOT true about viruses? (KMU MDCAT 2024)

  1. Contain DNA
  2. Can replicate on their own
  3. Can infect bacteria
  4. They have a sub-cellular structure
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Correct answer: (b) Can replicate on their own

A virus can only be copied inside a host cell, using the machinery of that cell.

22.Which of the following virus has a double stranded DNA genome? (NUMS MDCAT 2024)

  1. Rubella
  2. Influenza
  3. HIV
  4. Small pox
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Correct answer: (d) Small pox

The smallpox virus carries double stranded DNA; the other three are RNA viruses.

23.What of the following virus contains single stranded DNA? (UHS MDCAT 2023)

  1. Adeno virus
  2. Herpes virus
  3. Parvo virus
  4. Pox virus
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Correct answer: (c) Parvo virus

The parvoviruses are the smallest DNA viruses and their genome is a single strand.

24.How may tail fibrils are attached to the end plate of a bacteriophage? (UHS MDCAT 2023)

  1. 2
  2. 4
  3. 6
  4. 8
Show answer

Correct answer: (c) 6

Six tail fibres spread from the end plate and hold the phage to the bacterial wall.

25.All viruses are: (SZABMU MDCAT 2023)

  1. Autotrophs
  2. Heterotrophs
  3. Parasites
  4. Predators
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Correct answer: (c) Parasites

A virus can multiply only inside a living cell, so every virus is an obligate parasite.

26.The complete, mature and infectious virus particle is known as: (NUMS MDCAT 2023)

  1. Venome
  2. Genome
  3. Virion
  4. Capsid
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Correct answer: (c) Virion

A complete infectious virus particle is a virion.

27.Virus is what type of agent? (UHS MDCAT 2023)

  1. Cellular agent
  2. Infectious agent
  3. Non-infectious agent
  4. Non-protein agent
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Correct answer: (b) Infectious agent

A virus can do nothing but infect a living cell and multiply in it.

28.Viruses usually are limited to specific hosts because: (PMC MDCAT 2022)

  1. They contain either DNA or RNA
  2. They contain protein
  3. They are specific to cell receptors
  4. They are capable to divide with in the host body
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Correct answer: (c) They are specific to cell receptors

A virus can enter only a cell whose surface carries the receptor its coat proteins fit.

29.A virologist who studies viruses in great detail which of the following would he use? (PMC MDCAT 2022)

  1. Compound microscope
  2. Porcelain filters
  3. Electron microscope
  4. CT scan machine
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Correct answer: (c) Electron microscope

A virus is far below the resolving power of a light microscope.

30.Which of the following was the first virus to be isolated and studied under the electron microscope: (PMC MDCAT 2022)

  1. HIV
  2. Rabies Virus
  3. Pox Viruses
  4. TMV
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Correct answer: (d) TMV

Tobacco mosaic virus was the first virus isolated and the first seen under the electron microscope.

31.Which of the following is incorrect about virus? (PMC MDCAT 2022)

  1. Viruses are intracellular parasites
  2. Viruses cannot attack upon prokaryotes
  3. Viruses contain genetic information and have a capsid protein coat
  4. Viruses cannot survive without a host
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Correct answer: (b) Viruses cannot attack upon prokaryotes

Bacteriophages attack bacteria, which are prokaryotes.

32.The viruses who can attack the bacteria are known as: (PMC MDCAT 2022)

  1. Retrovirus
  2. Pox virus
  3. Bacteriophage
  4. Oncovirus
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Correct answer: (c) Bacteriophage

A virus that infects a bacterium is a bacteriophage.

33.Which of the following virus has complex capsid that consists of polyhedral head and helical tall? (PMC MDCAT 2022)

  1. Influenza virus
  2. Herpes virus
  3. Bacteriophage
  4. Human Immuno Deficiency virus
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Correct answer: (c) Bacteriophage

A T-even bacteriophage has a polyhedral head and a helical tail.

34.Poxviruses are: (PMC MDCAT 2022)

  1. Double stranded DNA virus
  2. Single stranded RNA virus
  3. Single stranded DNA virus
  4. Protein virus
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Correct answer: (a) Double stranded DNA virus

The poxviruses carry a large double stranded DNA genome.

35.A virus has its genome which is enclosed by a protein coat, called: (PMC MDCAT 2022)

  1. Spore
  2. Capsid
  3. Envelope
  4. Shell
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Correct answer: (b) Capsid

The protein coat round the viral genome is the capsid.

36.Viruses are able to recognize the host surface by means of their: (PMC MDCAT 2022)

  1. Capsid
  2. Spikes
  3. DNA
  4. RNA
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Correct answer: (b) Spikes

The spikes of the envelope fit the receptors of the host cell.

37.Which one can be considered as living characteristic of a virus: (NUMS MDCAT 2022)

  1. Can be crystallized
  2. No cellular respiration
  3. Mutate their genetic
  4. Lack biosynthetic machinery
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Correct answer: (c) Mutate their genetic

Mutation of its genetic material is the one thing a virus does that living things do.

38.What is the function of the lysozyme enzyme released by bacteriophages? (PMC Practice 2021)

  1. Injecting DNA
  2. Replication
  3. Dissolve bacterial cell wall
  4. All of these
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Correct answer: (c) Dissolve bacterial cell wall

The tail lysozyme digests a hole in the bacterial wall so the genome can be driven in.

39.What is the viral envelope composed of? (PMC Practice 2021)

  1. Proteins
  2. Glycoproteins
  3. Lipids and proteins
  4. All of the above
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Correct answer: (d) All of the above

The envelope is a piece of the host membrane, lipid and protein, with viral glycoprotein spikes in it.

40.Icosahedral Viruses have how many faces? (PMC Practice 2021)

  1. 20
  2. 30
  3. 10
  4. 40
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Correct answer: (a) 20

An icosahedron has twenty triangular faces.

41._________ refers to the breakdown or removal of the capsid. (PMC Practice 2021)

  1. Assembly
  2. Uncoating
  3. Integration
  4. Maturation
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Correct answer: (b) Uncoating

Uncoating is the stripping of the capsid that frees the viral genome inside the host cell.

42.Which of the following is not related to the enveloped virus? (PMC MDCAT 2020)

  1. They survive for a long time
  2. Their envelope is not sensitive to sunlight
  3. They are tolerant to antibodies
  4. Envelope is derived from host
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Correct answer: (b) Their envelope is not sensitive to sunlight

The lipid envelope is easily damaged by sunlight, drying and detergents.

43.The complete, mature and infection virus particle is known as: (PMC MDCAT 2020)

  1. Venome
  2. Genome
  3. Virion
  4. Capsid
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Correct answer: (c) Virion

A complete infectious virus particle is a virion.

44.The protein coat of virus is called: (UHS MDCAT 2019)

  1. Capsid
  2. Cosmid
  3. Capsomere
  4. Chromophore
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Correct answer: (a) Capsid

The protein coat of a virus is its capsid.

45.In viruses, a combined structure formed by core (Nucleic Acid) and capsid is: (UHS MDCAT 2018)

  1. Nucleocapsid
  2. Prion
  3. Envelope
  4. Capsomeres
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Correct answer: (a) Nucleocapsid

The genome with its capsid together are the nucleocapsid.

46.Phages which show lysogenic cycle are known as: (UHS MDCAT 2018)

  1. Enveloped Phage
  2. Virulent Phage
  3. Temperate phages
  4. Bacteriophage
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Correct answer: (c) Temperate phages

A temperate phage integrates its genome and lies dormant instead of bursting the cell at once.

47.Size of virus ranges in: (UHS MDCAT 2017)

  1. 20 to 250 nm
  2. 25 to 250 nm
  3. 25 to 300 nm
  4. 20 to 300 nm
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Correct answer: (a) 20 to 250 nm

Viruses run from about $20$ to $250\,\mathrm{nm}$ across.

48.All viruses can reproduce within living organisms only, so they are known as: (UHS MDCAT 2016)

  1. Ectoparasites
  2. Endoparasites
  3. Obligative Intracellular Parasites
  4. Facultative Intracellular Parasites
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Correct answer: (c) Obligative Intracellular Parasites

A virus can multiply only inside a living cell, so it is an obligate intracellular parasite.

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