BLS 113 UE July 2022

SOKOINE UNIVERSITY OF AGRICULTURE

COLLEGE OF VETERINARY AND MEDICAL SCIENCES

UNIVERSITY EXAMINATION FOR 1st YEAR BACHELOR OF BIOTECHNOLOGY AND LABORATORY SCIENCES

DATE: 14th July 2022

TIME: 3:30-6:30 pm

INSTRUCTIONS: ATTEMPT ALL QUESTIONS
Use well labeled diagrams where necessary

VENUE:

QUESTION ONE (25 Marks)
a) List FOUR kinds of subviral agents and state why EACH of these subviral agents does not comply with the classical definition of a “virus.” (8 marks)
b) List TWO characteristics that viruses share with living organisms and explain why viruses do not fit our usual definition of life (7 marks)
c) Briefly describe how each of the seven groups of viruses (based on Baltimore classification) fit into the central dogma of life (10 marks)

QUESTION TWO (25 Marks)
a) Describe four shapes of viruses based on their symmetry (8 marks)
b) State why bacteriophages are more complex than typical icosahedral or helical viruses (5 marks)
c) What are the functions of the capsid? (6 marks)
d) Name and describe THREE viral properties that are used to classify viruses? (6 marks)

QUESTION THREE (25 Marks)
The figure below represents a replication cycle of an enveloped negative sense single-stranded RNA virus. Use it to answer the questions below it.

a) The virus in the figure above starts its replication cycle by attaching to a receptor on the plasma membrane of host cell. Why would a cell possess a receptor that the virus could adsorb to? (4 marks)
b) Name the processes taking place at A, B, C, D, E and F (6 marks)
c) Briefly describe how the viral genome, mRNA and proteins are synthesized by the virus represented in the figure above? (9 marks)
d) How does the virus in the figure above obtain its envelope? (6 marks)

QUESTION FOUR (25 Marks)
a) Name any FIVE routes of viral entry into the body and any THREE routes for virus shedding (8 marks)
b) Can viruses replicate in the skin? Why or why not? (2 marks)
c) Describe any FOUR ways viruses can damage infected host cells (12 marks)
d) What are the THREE commonly proposed mechanisms for the origins of viruses? (3 marks)

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