VM 232 CAT June 2013

DEPARTMENT OF VETERINARY MICROBIOLOGY AND PARASITOLOGY

VM232 (VIROLOGY PART) CAT; TIME 2 HRS (21st June, 2013)

MULTIPLE CHOICE QUESTIONS (Each 2 marks)
Identify the choice that best completes the statement or answers the question by making a circle of the correct choice.

A: Introductory part
1. The host range of a virus is determined by
A) the enzymes carried by the virus. B) whether its nucleic acid is DNA or RNA.
C) the proteins in the host’s cytoplasm. D) the enzymes produced by the virus before it infects the cell. E) the proteins on the capsid and the proteins on host cell membranes.

2. Viruses differ from bacteria in that all viruses —
A) cause insect-borne diseases B) can be destroyed by antibiotics
C) have rigid cell walls D) must be reproduced in living cells

3. Which of the following statements about viruses is false?
A) They come in many different shapes and sizes B) They contain genetic material, protein and a few organelles C) Each type of virus can only infect specific hosts
D) Different viruses infect hosts from all of the 5 kingdoms of life

4. Most scientists think that early viruses originated from
A) other viruses. B) existing cell parts. C) animals. D) spontaneous generation.

B: Characteristics of viruses
5. One characteristic shared by a virus and a living cell is that both —
A) store genetic information in nucleic acids B) have a crystalline structure C) gain energy directly from the sun D) use glucose for respiration

6. Which of the following is a characteristic of all viruses?
A) nucleic acid genome B) a protein capsid C) glycoprotein cell wall D) A and B only E) A, B, and C

7. Viruses are referred to as obligate parasites because
A) viral DNA inserts itself into host DNA. B) they reproduce and then exit the cell.
C) they are non-living. D) they use the host’s energy to live.
E) they use the host cell’s nucleotides and enzymes to reproduce.

8. Which of the following is a true statement about viruses?
A) A single virus particle contains both DNA and RNA. B) Viruses are classified below the cellular level of biological organization. C) Even small virus particles are visible with light microscopes.
D) A and B only are true. E) A, B, and C are true.

9. Viruses are considered nonliving because
A) they cannot reproduce by themselves. B) they are not made up of cells.
C) they cannot carry out metabolism by themselves. D) All of the above

C: Structure of viruses
10. What is the basic structure of a virus?
A) DNA or RNA surrounded by a protein coat B) a capsid surrounded by a protein coat
C) a bacteriophage surrounded by a membrane D) a tiny cell surrounded by a cell wall

11. Viral envelopes are generally
A) made of peptidoglycan cell wall material. B) composed of a lipid bilayer.
C) found between the viral protein coat and its DNA. D) composed of protein.
E) composed of single-stranded RNA.

12. The capsid of a virus is the
A) protective outer coat. B) cell membrane. C) nucleus. D) cell wall and membrane complex.

Figure 1

13. Refer to figure 1 above. Which structure could possibly be made of RNA?
A) structure 2 C) structure 4 B) structure 3 D) structure 5

14. Refer to figure 1 above. Which structure is found outside the cell after the cell is
infected?
A) structure 1 C) structure 3 B) structure 2 D) structure 4

15. Proteins in the viral capsid or on the surface membrane function to
A) bind the virus to the surface of a host cell. B) transcribe viral genes.
C) force a host cell to make copies of the virus. D) destroy a host cell.

D: Classification and nomenclature
16. Viruses are classified according to
A) whether they contain RNA or DNA. B) the shape of their genome.
C) whether they have a membrane envelope. D) All of the above

17. Rift valley fever virus was named based on
Morphology B) Location in the host’s body C) Geographical location D) Type of lesion

E: Replication cycle
18. Which of the following methods is used by a non-enveloped virus to enter a cell:
A) plasma membrane fusion B) endocytosis C) integration D) pore formation

19. In order for a DNA virus to replicate inside a cell, what part(s) of the virus must enter the cell?
A) The nucleic acid material B) The capsid C) Reverse transcriptase D) RNA-dependent RNA polymerase E) cRNA

20. Which viruses always have an RNA chromosome that acts as a template for DNA synthesis?
A) lytic phages B) proviruses C) prokaryotes D) bacteriophages E) retroviruses

21. What is the function of reverse transcriptase in retroviruses?
A) It hydrolyzes the host cell’s DNA. B) It uses viral RNA as a template for DNA synthesis.
C) It converts host cell RNA into viral DNA. D) It translates viral RNA into proteins.
E) It uses viral RNA as a template for making complementary RNA strands.

22. When a bacteriophage attaches to a bacteria cell,
A) The whole bacteriophage enters the cell B) Only the nucleic acid materia enters the cell
C) Only the capsid coat enters the cell D) No parts of the bacteriophage enters the cell

 

 

23. The virus to the right must have a………………………………… life cycle.

A) haplontic B) diplontic C) lytic
D) lysogenic E) none of these

 

 

 

24. During the lytic stage of a viral life cycle:

A) the host cell produces many viruses B) the host cell lyses C) the host cell is able to destroy the virus D) the host cell goes into a type of dormancy
E) the host cell accepts the viral DNA into it’s own genome

F: Pathogenecity of viruses
25. Most viruses infect a specific kind of cell. Which of the following are infected by the human immunodeficiency virus (HIV)?
A) Helper T cells B) Liver cells C) GABA-receptor cells D) Red blood cells

26. A lysogenic virus could cause cancer by
A) Producing toxins that are poisonous to the body B) Causing all of the reproducing cells to lyse
C) Insertion of the prophage into a gene that controls cell division D) Carrying a gene that codes for an essential amino acid E) None of these; viruses cannot cause cancer

27. HIV causes AIDS by
A) converting a proto-oncogene to an oncogene. B) damaging a person’s blood vessels.
C) destroying the covering of a person’s nerves. D) gradually destroying a person’s immune system.

G: Epidemiology and control of viruses
28. Which of the following explains why antibiotics can treat flu-like symptoms caused by bacteria but are ineffective against flu?
A) Flu is a response to an antigen. B) Antibiotics require time to work.
C) Antibiotics strengthen antibodies. D) Flu is caused by a virus.

29. Antibiotics are ineffective against viral infections because
A) host cells protect the viruses. B) viruses have enzymes that inactivate the antibiotics.
C) antibiotics interfere with cellular processes that viruses do not perform.
D) viral protein coats block the antibiotics from entering the virus.

30. Viral diseases can be
A) treated with antibiotics and prevented with vaccines. B) treated with vaccines and prevented with antibiotics. C) prevented with antibiotics but not treated with vaccines.
D) prevented with weakened or killed vaccines but not treated with antibiotics.

SLIGHT DETAILLED QUESTIONS (Be brief and to the point)

1. With examples, write short notes on criteria for classifying and naming of viruses. 16 marks
2. State two problems faced by viruses with RNA genomes, and explain how these viruses address these challenges. 4 marks
3. What does (+) and (‐) strand RNA mean in viral genomes? 4 marks
4. Select a virus family of your interest and describe it under the following headings
a) General structure (virion size, genome type and size, capsid type and envelope) 5 marks
b) One disease of veterinary importance (hosts, transmission clinical signs, laboratory diagnosis, control) 6 marks
c) Virus replication (target cell, host receptors, viral ligand, mode of entry into a cell) 5 marks