SOKOINE UNIVERSITY OF AGRICULTURE
COLLEGE OF VETERINARY MEDICINE AND BIOMEDICAL SCIENCES
VM 235: VETERINARY VIROLOGY CAT 1
TIME ALLOWED: 1 HOUR DATE: 27-11-2022
Instructions:
- This paper has TWO printed pages containing THREE questions
- Answer ALL THREE questions (Total 82 marks)
- ALL answers to ALL questions MUST be written in the respective spaces provided in each question
1. Briefly, answer the following questions (i-x) in relation to viruses (Total 32 marks)
i. Why viruses are referred to as obligate intracellular parasites? (2 marks)
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ii. Why do viruses have smaller size than bacteria (3 marks)
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iii. Mention one structural part found in all viruses? (2 marks)
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iv. Viruses have some of the properties of living organisms. State one characteristic shared by a virus and a living cell (3 marks) …….………………………………………………………..
v. What determines the host range of a virus? (3 marks)
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vi. Why RNA viruses are prone to mutations? (3 marks)
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vii. Which group of viruses always have an RNA genome that acts as a template for DNA synthesis? (2 marks) ……………….………………………………………………………….
Why do these viruses synthesize DNA? (3 marks) …..………………………………………..
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viii. Why do RNA viruses require their own supply of certain enzymes in their replication cycles? (3 marks).………………………………………………………………………………
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ix. The synthesis of viral proteins for all viruses is carried out in the cytoplasm. Why is it so? (3 marks) …………………………………………………………………………………………
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x. In the (–) sense RNA genomes, the (+) strands and mRNA are the same. True or False? (2 marks) Why or why not? (3 marks) …………………………………………………………………………………………………..
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2. Using the figure below, indicate how the SEVEN groups of virus genomes (based on Baltimore classification) fit into the central dogma of life (7 marks) and indicate using arrows how they proceed towards making protein (7 marks).
3. By filling in the table provided below (Each 1 mark, Total 36 marks);
i. Name the virus groups based on Baltimore classification
ii. Provide the sites where replication of the genome and transcription takes place
iii. State whether the virus group packages enzyme (s) within the virion or not (Write Yes or No)
| Baltimore Class | Virus group | Site for genome replication | Site for transcription | Package enzyme (s) |
| Class I (smaller) | ||||
| Class I (larger) | ||||
| Class II | ||||
| Class II | ||||
| Class IV | ||||
| Class V (segmented) | ||||
| Class V (non-segmented) | ||||
| Class VI | ||||
| Class VII |
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