Virology Multiple Choice Questions & Answers (MCQs) focuses on “Structure of Viruses”.
1. Viruses, outside their host cells, survive as ____________
a) bacteria
b) virions
c) algae
d) protozoa
Answer: b
Clarification: The viruses outside their host cells survive as virus particles, which is also known as virions. The virion contains the viral genome and is a gene delivery system.
2. The viral genome is packaged into a structure made of ______________
a) protein
b) carbohydrate
c) fats
d) lipids
Answer: a
Clarification: The viral genome is packaged into a structure made up of protein. This outer protein structure is known as a capsid. Its main function is to protect the viral nucleic acid from digestion by enzymes.
3. Which of the following is not the category of virus genome?
a) dsDNA
b) ssRNA
c) tsDNA
d) dsRNA
Answer: c
Clarification: All the nucleic acids exist as double-stranded (ds) or single-stranded (ss). Thus, it gives four categories of virus genome: dsDNA, ssDNA, dsRNA, ssRNA.
4. Most of the plant viruses have ____________
a) ssRNA
b) ssDNA
c) dsDNA
d) dsRNA
Answer: a
Clarification: The majority of the plant viruses have single-stranded RNA as their genome, while most of the fungal viruses have double-stranded RNA and most prokaryotic viruses have double-stranded DNA genomes.
5. Which of the following organism contains the largest genome size?
a) HBV
b) Phage lambda
c) Mimivirus
d) Mycoplasma genetalium
Answer: c
Clarification: Mimivirus possesses the largest genomic size of about 1200 kilobase pairs of DNA. The phage lambda possesses 48.5 kbp, HBV possesses 3.2 kbp and Mycoplasma genetalium possesses 580 kbp DNA.
6. Which of the following virus possess a single-stranded, linear genome?
a) TMV
b) Poxvirus
c) Baculovirus
d) Reovirus
Answer: a
Clarification: The tobacco mosaic virus (TMV) possesses a single-stranded, linear RNA genome. Whereas poxvirus possesses double-stranded, linear genome, baculovirus possesses double-stranded, circular genome and reovirus has a double-stranded, linear genome.
7. Which of the following is the most common capsid shape of the virus?
a) Cube
b) Rod
c) Cone
d) Icosahedron
Answer: d
Clarification: The most common capsid shape of the virus is icosahedron and helical symmetries. Some of the examples of symmetrical structures are rod, helix, cone, and icosahedron. An icosahedron is an object or symmetry with 20 faces, 12 vertices, and 30 edges.
8. The number of subunits in a virus particle is given by _________
a) T = Pf
b) P = Tf
c) T = Pf2
d) T = Pf3
Answer: c
Clarification: The number of subunits in a virus particle is given by T = Pf2, where T is the triangulation number. P is given by the expression h2 + hk + k2. In this expression, h and k are any pair of integers without common factors, i.e. h and k cannot be multiplied or divided by any number to give the same values, f = 1, 2, 3, 4, etc.
9. Which of the following virus have virions with internal lipid membranes?
a) Rabies virus
b) Influenza virus
c) Ebola virus
d) Iridovirus
Answer: d
Clarification: Iridoviruses are viruses that have a lipid membrane within the virion rather than at the surface. Other examples include tectiviruses and chlorella virus. Rabies, Influenza, and Ebola viruses have lipid membranes at the surface of the virion.
10. The viral envelope is made up of protein bilayer.
a) True
b) False
Answer: b
Clarification: The viral envelope is made up of the lipid component, which is present at the surface of virion or present within the virion. It protects the capsid and may help viruses avoid the host immune system.
11. The viral genome contains non-repeated sequences.
a) True
b) False
Answer: b
Clarification: The genome of viruses contains several repeated sequences which include promoters, enhancers, the origin of replication, and other important elements that are involved in the control of events in the replication of the virus.