1. Who discovered viruses?
a) Beijerinck
b) Iwanowski
c) Twort
d) Ellerman
Explanation: Dmitri Iwanowski, in the year 1892, discovered the viruses. He found the causal agent of mosaic disease of the tobacco plant which caused the discoloration of the leaf. He was one of the founders of virology.
2. Who reported the cell-free transmission of chicken leukemia?
a) Ellerman and Bang
b) Loeffler and Frosch
c) Iwanowski and Beijerinck
d) Twort and Bang
Explanation: Ellerman and Bang, in the year 1908, reported the cell-free transmission of chicken leukemia whereas Rous in 1911 discovered that the solid tumors of chicken could be transmitted by cell-free filtrates. These were the first indications or observations that the viruses can be carcinogenic.
3. The bacteriophages were discovered by ____________
a) Beijerinck
b) Iwanowski
c) Twort
d) Ellerman
Explanation: The bacteriophages or bacterial viruses were discovered by Frederick William Twort in 1915. The bacteriophages are the viruses that infect, multiply, and then finally kill the bacteria.
4. The one-step growth curve was used to study ____________
a) the development of viral assays
b) the discovery of viruses
c) the multiplication of viruses
d) the origin of viruses
Explanation: The one-step growth curve was used to study the multiplication cycle of viruses in a host organism or bacteria. The experiment was performed by Ellis and Delbruck in 1939 where a bacteriophage lambda was mixed in a suspension of Escherichia coli and the multiplication of virus was studied.
5. Which of the following is not the phase of the one-step growth curve?
a) Eclipse phase
b) Maturation phase
c) Latent phase
d) Luteal phase
Explanation: There are three phases of one-step growth curve: eclipse phase, maturation phase, and latent phase. Whereas, the luteal phase is the phase of the menstrual cycle.
6. Which of the following phase measures the period before the infectious virus is released into the medium?
a) Eclipse phase
b) Luteal phase
c) Latent phase
d) Maturation phase
Explanation: The latent phase measures the period before the infectious virus is released from the cells into the medium. During the eclipse phase, the infectivity of the cell-associated infecting virus is lost as it uncoats and during the maturation phase, infectious virus is assembled inside the cells.
7. Who isolated TMV in paracrystalline form?
a) Stanley
b) Bawden
c) Pirie
d) Schlessinger
Explanation: Stanley, in the year 1935, isolated the tobacco mosaic virus or TMV in paracrystalline form. Schlessinger purified the virus by using differential centrifugation, Bawden and Pirie purified TMV and showed it to be containing ribonucleic acid (RNA).
8. The genetic material of bacteriophage T2 is __________
a) RNA
b) DNA
c) Carbohydrate
d) Protein
Explanation: The genetic material of bacteriophage T2 is DNA and the evidence of DNA as genetic material was given by Hershey-Chase experiment.
9. Viruses do not have a protein coat.
a) True
b) False
Explanation: Viruses have the protein coat whereas viroids are the agents that have no protein coat. They are smaller than viruses and are composed of a short strand of circular, single-stranded RNA.
10. Which of the following phase determines the specificity of the virus?
a) Penetration
b) Attachment
c) Release
d) Uncoating
Explanation: The attachment phase determines the specificity of the virus for a particular type of host species. Once the attachment is done, it is followed by penetration, uncoating, biosynthesis, assembly and finally, the release of phage particles.