This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Viruses of Bacteria – Morphology and Structure of Phages”.
1. The nucleic acid core of phages is covered by a protein coat known as _______________
c) outer envelope
d) nuclear membrane
Explanation: All phages have a nucleic acid core covered by a protein coat or capsid. The capsid is made up of morphological subunits called capsomeres.
2. The most complex type of bacterial virus has which of the following morphological features?
a) hexagonal head and tail fibres
b) no contractile sheath
c) hexagonal head but no tail
d) hexagonal head, rigid tail with contractile sheath
Explanation: The most complex type has a hexagonal head, a rigid tail with a contractile sheath, and tail fibers.
3. Which of the following is true for the bacteriophage MV-L2?
a) head is made up of large capsomeres
b) head is made up of small capsomeres
c) no contractile sheath is present
d) filamentous form
Explanation: Bacteriophage MV-L2 has a filamentous form. This type is found in some plant viruses.
4. Pleomorphic viruses possess double-stranded DNA.
Explanation: Pleomorphic viruses were recently discovered to have a lipid-containing envelope, have no detectable capsid, and possess double-stranded DNA (ds-DNA).
5. What is the shape of helical phages?
a) regular solids
Explanation: Helical phages are rod-shaped whereas cubical phages are regular solids or more specifically polyhedra.
6. Which of the following are said to have binal symmetry?
Explanation: T-even coliphages such as T2, T4, and T6, are said to have binal symmetry because each virion has both an icosahedral head and a hollow helical tail.
7. The DNA of phage lambda is circular both in the virion and in the host cell.
Explanation: The DNA of phage lambda is linear in the virion, but on entering the host cell the cohesive ends join to form a circle.
8. Which of the following is a family of lambda phage viruses?
Explanation:Styloviridae is a family of lambda phage viruses that are non-enveloped and has dsDNA.
9. Which of the following coliphage has tadpole shape?
Explanation: T3 and T7 have tadpole shapes and the tails are very short. All others have polyhedra heads and long tails.
10. Which of the following are filamentous phage of E.coli?
c) f1 and fd
d) T3 and T7
Explanation: Filamentous phages of E.coli include f1 and fd bacteriophages. They all have circular single-stranded DNA.
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