This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Structure and Composition”.
1. Which of the following symmetry is exhibited by rod-shaped viruses?
Explanation: The animal and plant viruses are composed of a central core of nucleic acid surrounded by a capsid, which is made up of capsomeres. They exhibit a characteristic symmetry like the rod-shaped viruses have a helical symmetry.
2. The envelope surrounding the nucleocapsid of some animal viruses is made up of which of the following structures?
Explanation: In some animal viruses the nucleocapsid is covered by an outer membranelike structure called the envelope, which is made up of lipoproteins and conceals the symmetry.They are sensitive to lipid solvents such as ether and chlorofoam.
3. Adenoviruses exhibit which of the following symmetry?
a) helical symmetry
b) circular symmetry
c) icosahedral symmetry
d) complex structure symmetry
Explanation: Adenoviruses which cause respiratory infections are examples of icosahedral viruses.
4. The fringes on animal viruses like influenza virus is made up of ______________
Explanation: In the influenza virus the nucleocapsid is a flexible structure packed within a fringed lipoprotein envelope.The fringes are actually spiked projections made of glycoproteins.
5. Animal and plant viruses contain both DNA and RNA in the same virion.
Explanation: Like bacteriophages, animal and plant viruses contain either DNA or RNA, but never both in the same virion.
6. Parvoviruses contain how many genes?
a) 100 genes
b) 500 genes
c) 40 genes
d) 3 genes
Explanation: If 1 kilobase is considered as the size of an average gene, small viruses like parvoviruses and picornaviruses contain perhaps 3 or 4 genes and large viruses contain several hundred.
7. In papovaviruses, DNA occurs in which of the following forms?
a) linear dsDNA
b) linear ssDNA
c) supercoiled circular dsDNA
d) supercoiled circular ssDNA
Explanation: In papovaviruses, DNA occurs as a supercoiled circular dsDNA.Supercoiling refers to the extra turns in the structure of dsDNA due to the action of the enzyme DNA gyrase.
8. In which of the following viruses DNA forms hairpins?
Explanation: In ssDNA parvoviruses the terminal bases of linear DNA exist as inverted repeat sequences that form hairpins.That is, the sequence of terminal bases on each strand of such DNA maybe represented as ABCD…….D’C’B’A’, where ABCD are complementary to A’B’C’D’.
9. RNA in animal viruses exist as circular dsRNA.
Explanation: Some plant viruses appear to have a genome of circular dsRNA.But the RNA in animal viruses exists only as linear double-stranded or single-stranded molecules.
10. Which of the following are characteristics of the process viropexis?
a) phagocytic process
b) plant viruses penetrate host cells through ectodesmata
c) occurs by the enzyme RNA polymerase
d) phagocytic process and occurs by the enzyme lysosomal proteases
Explanation: Engulfment of whole virions by the cells occurs in a phagocytic process called viropexis, followed by uncoating or removal of the capsid.This takes place in th phagocytic vacuoles and is due to the action of the enzymes called lysosomal proteases.
11. Which of the following viruses carry minus-strand RNA?
d) tobacco mosaic viruses
Explanation: RNA viruses like rhabdoviruses,orthomyxoviruses,paramyxoviruses carry minus-strand RNA and they must first transcribe their RNA to form the plus strand that can function as mRNA. This transcription is catalyzed by a viral RNA polymerase.
Sanfoundry Global Education & Learning Series – Microbiology.
To practice all areas of Microbiology, here is complete set of 1000+ Multiple Choice Questions and Answers.