VM 235 Probation 2022

SOKOINE UNIVERSITY OF AGRICULTURE

            COLLEGE OF VETERINARY AND MEDICAL SCIENCES

 PROBATION/FIRST SITTING FOR 2^rd YEAR BACHELOR OF VETERINARY MEDICINE

Course Ante:   VM 235  Course Title:  VETERINARY VIROLOGY

DATE:  29^th September 2022                      TIME: 15:00-18:30 HRS

 INSTRUCTIONS: ATTEMPT ALL QUESTIONS

                          Use well labeled diagrams where necessary                                  

      VENUE:                                                                         

QUESTION ONE (22 Marks)

Write a word or phrase that best fits in the blank spaces provided (2 marks each)

a) The component(s) of a virus that is/are extended from the envelope for attachment is/are the……………………………………………

b) The envelope of a virus is derived from the host’s ……… ……….

c) In naming viruses, the family name ends with ………………… and genus name ends with……………………………………………….

d) A/an ……………virus possesses characteristics of both an icosahedral and a helical virus.

e) A virus containing only nucleic acid and a capsid is called a/an ……………virus or ………………………. virus.

f) The ……………………. on the bacteriophage allow for binding to the bacterial cell.

g) The integrated HIV dsDNA into the host genome becomes permanent part of the host genome and is called…………………………………

h) The form of a virus when is inside the cell is called…………………. and when the virus is outside the cell is called……………………….

i) Virus replication cycle is also called…………………………………..

j) The virus always will attach to the …………. present on the surface of cell using…………. present on the surface of the virus

k) Receptor-mediated endocytosis is one of the main mechanisms used by enveloped viruses to……………………………………………….

QUESTION TWO (25 Marks)

a) Using a well labelled diagram, illustrate and describe functions the most important components of the ‘typical’ virus particle (14 marks)

b) What are the three major types of symmetry associated with viral particles and what shape do the respective particles assume? (6 marks)

b) Provide one example of viruses for each of the three types of symmetry (3 marks)

b) Which two of the three types of symmetry are most commonly found? (2 marks)

QUESTION THREE (28 Marks)

The figure below represents a replication cycle of Foot-and-mouth disease (FMD) virus, a causative agent of a highly contagious disease of domestic animals including cattle, pigs, sheep and goats. Use the figure to answer all the questions below it.

a) In which family do the virus belong? (2 marks)

b) What criterion was used to name the viruses under the family? (2 marks)

c) Classify the virus based on the outer covering and capsid symmetry (4 marks)

d) Name the replication steps labelled 1, 2, 4, 9, 12 and 13 (6 marks)

e) Why does the virus replicate only in the cytoplasm? (4 marks)

f) How does the virus leave the infected cell after replication? (3 marks)

g) Which ones in the figure above are structural and non-structural proteins among the following: P1, P2, P3, VP0, VP1, and VP2 (5 marks)

h) Explain why FMD virus is prone to mutations? (4 marks)

QUESTION FOUR (25 Marks)

Most DNA viral genomes must enter the nucleus for replication while few DNA viral genomes replicate in the cytoplasm.

a) Explain this difference (6 marks)

b) State the problem that is created to DNA viruses which replicate in the cytoplasm (4 marks)

c) Explain how the viruses that replicate in the cytoplasm overcome this problem (6 marks)

d) All RNA viruses encode their own replication system. True or False? Why? (4 marks)

e) In the (–) sense RNA genomes, the (+) strands and mRNA are the same. True or False? Why or why not? (5 marks)

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