SOKOINE UNIVERSITY OF AGRICULTURE
COLLEGE OF VETERINARY AND MEDICAL SCIENCES
PROBATION/FIRST SITTING EXAMINATION FOR 1st YEAR BACHELOR OF BIOTECHNOLOGY AND LABORATORY SCIENCES
DATE: 14th October 2022
TIME: 08:00-11:00 pm
INSTRUCTIONS: ATTEMPT ALL QUESTIONS
Use well labeled diagrams where necessary
VENUE:
QUESTION ONE (25 Marks)
Using a tabular form, provide the differences between the following terminologies and/ or phrases: (5 marks each)
a) A virus versus a provirus
b) A virion versus a prion
c) A viroid versus a virusoid
d) A susceptible cell versus a permissive cell
e) A positive-sense RNA virus versus a negative-sense RNA virus
QUESTION TWO (25 Marks)
a) Explain why viruses are obligate intracellular parasites? (4 marks)
b) Describe FOUR reasons why it is important to study viruses (8 marks)
c) What hypotheses exist for the origin of viruses and which do you think is most likely, and why? (6 marks)
QUESTION THREE (25 Marks)
a) What is the difference between a capsid, nucleocapsid and an envelope of a virus (6 marks)
b) Name the parts labelled A, B, C and D in the figure below (6 marks)
c) Provide any ONE function of part A, B, and C in the figure below (6 marks)
d) Name ONE type of cell infected by the viruses represented in the figure below (3 marks)
e) How does the genome of the virus in the figure below released into the cell it infects? (4 marks)
QUESTION FOUR (25 Marks)
a) Describe chronologically all the SEVEN steps of virus infectious cycle (14 marks)
b) What is the role (s) of virus genome in the virus replication cycle? (5 marks)
c) Explain what generally determines whether or not a virus needs to gain entry into the nucleus for replication? (6 marks)
****************************************BEST WISHES************************************************************