This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Cell Introduction – Viruses and Viroids”.
1. The following diseases is caused by viruses ____________
a) Influenza
b) Measles
c) Typhoid
d) Both Influenza and Measles
View Answer
Explanation: Measles and Influenza are diseases caused by the infection of viruses. Typhoid is caused by a bacteria known as Salmonella typhi.
2. Which of the following is not true for TMV Virus?
a) It does not contain spikes
b) TMV Virus affects tobacco plants
c) It contains viral coat containing copies of multiple proteins
d) It is a retrovirus
View Answer
Explanation: TMV or Tobacco Mosaic Virus causes viral infection to the tobbacco plant. It is a rod-shaped helical RNA virus which consists of a single strand of RNA placed centrally enveloped by a protein coat.
3. Which of the following is the largest bacteriophage?
a) T4 bacteriophage
b) T6 bacteriophage
c) Lambda phage
d) T2 bacteriophage
View Answer
Explanation: T4 bacteriophage is among the largest bacteriophages. It is approximately 90-100 nm wide and 200 nm long. Its double stranded DNA genome is about 169 kb long and encodes 289 proteins.
4. The integrated genetic material of a virus is called __________________
a) Viroid
b) Provirus
c) Virus-like-particle (VLP)
d) Prion
View Answer
Explanation: The virus infection is caused by the entry of entry of viral DNA into the host cell. After this, the viral DNA is integrated into the host genome. This viral genetic material incorporated into host genome and able to replicate itself is called as provirus.
5. Virus like particles (VLP) are ____________
a) Immunogenic and infectious
b) Immunosuppressive and infectious
c) Infectious but not immunogenic
d) Immunogenic but not infectious
View Answer
Explanation: An immunogenic organism can evoke the immune response when entered inside a host. Immunosuppressive organism can suppress the host immune response and infectious organism can cause infection to the host. VLP or Virus like particles are the outer protein covering of the virus with no viral genetic material. Hence, they can evoke host immune response but cannot cause infection to the host.
6. Which of the following viruses have DNA as its genetic material?
a) Tobacco Mosaic Virus
b) Potato Mosaic Virus
c) Tomato Mosaic Virus
d) Cauliflower Mosaic Virus
View Answer
Explanation: Cauliflower Mosaic virus is a DNA virus with a nucleotide sequence of 8024 nucleotides. Tobacco Mosaic Virus, Potato Mosaic Virus and Tomato Mosaic Virus are retroviruses with RNA as its genetic material.
7. HIV antagonizes the ___________ cell in human body.
a) Red Blood Cell (RBC)
b) Cytotoxic T cell
c) B cell
d) Helper T cell
View Answer
Explanation: HIV or Human Immune deficiency Virus infects the Helper T cells present in the blood. It recognizes the CD4 proteins on the surface of the helper T cells and thus infects it. By doing this, HIV manipulates the very cells which activate both B cells and Cytotoxic T cells.
8. Which of the following has the largest DNA sequence?
a) Pithovirus sibericum
b) Megavirus chilensis
c) TMV
d) T4 bacteriophage
View Answer
Explanation: Megavirus chilensis has the largest genome length of 1,259,197 base-pair with around 1120 proteins. Pithovirus sibericum is currently the largest known virus with a length of 1500 nm and diameter 500 nm.
9. Which of the following enables a Dengue virus to affect human beings?
a) RNA Polymerase enzyme
b) DNA Polymerase enzyme
c) Reverse Transcriptase enzyme
d) Gyrase enzyme
View Answer
Explanation: The Dengue Virus is a retrovirus which contains RNA as its genetic material. So, to infect a human being by integrating its genome into the human DNA genome, it is necessary to convert its RNA sequence into DNA. Reverse Transcriptase enzyme catalyzes the reverse transcription of viral RNA into DNA.
10. Viruses can be cultivated in_________________
a) Whole plant
b) Cell lines
c) Chick Embryo
d) All of the mentioned
View Answer
Explanation: Viruses need a living system to survive and replicate. They complete their life cycle inside the living host but otherwise remain inert. Whole plant, cell lines and chick embryo act as appropriate living systems for the virus.
11. The capsomeres contain small protein subunits known as ___________________
a) Protomeres
b) Capsoproteins
c) Prions
d) None of the mentioned
View Answer
Explanation: Capsomeres are the subunits of the protein coat enveloping the viral genome known as the Capsid. The Capsomeres assemble to form the capsid and are in turn made up of an assembly of smaller protein subunits known as Protomeres.
12. Which of the following viruses is found in saliva?
a) HIV
b) Dengue virus
c) Hepatitis B virus
d) Epstein-Barr virus (EBV virus)
View Answer
Explanation: Epstein-Barr virus or EBV is also known as Herpes virus 4. It causes an infection called Mononucleosis, which is a contagious disease. Since the virus is present in the saliva of the host, it can be contracted by a healthy individual by kissing or eating from the same utensils.
13. How many structural and non-structural proteins are there in the dengue virus?
a) 7 ; 2
b) 3 ; 8
c) 3 ; 7
d) 3 ; 9
View Answer
Explanation: Dengue virus has 3 structural or surface proteins namely the Capsid protein (C), the Membrane protein (M) and the Envelope protein (E). It also has 7 non-structural proteins (NS proteins) namely NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5.
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