BLS 108_CAT 2_2020

SOKOINE UNIVERSITY OF AGRICULTURE

COLLEGE OF VETERINARY MEDICINE AND BIOMEDICAL SCIENCES
DEPARTMENT OF MICROBIOLOGY, PARASITOLOGY AND BIOTECHNOLOGY

BLS 108: VIROLOGY CAT 2
TIME ALLOWED: 1 HOUR DATE: 05-08-2020
Instructions:
1. This paper has FOUR printed pages with three sections (A, B and C)
2. Answer ALL NINE questions
3. ALL answers to ALL questions MUST be written in the respective spaces provided in each question
4. Read instructions carefully before beginning each section and each question

SECTION A (30 marks)
1. Select the best answer among the alternative statements given for each question and circle it (20 marks)

i. Which of the following internalization method is mostly used by enveloped viruses to enter a cell:
A) plasma membrane fusion B) endocytosis
C) integration D) pore formation

ii. In order for a virus to replicate inside a cell, what component of the virus must enter the cell?
A) the genome B) the capsid C) Reverse transcriptase
D) RNA-dependent RNA polymerase E) cRNA

iii. Which viruses always have an RNA genome that acts as a template for DNA synthesis?
A) lytic phages B) retroviruses C) hepadnaviruses
D) bacteriophages E) all of the above

iv. 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

v. RNA viruses require their own supply of certain enzymes because
A) host cells rapidly destroy the viruses
B) host cells lack enzymes that can replicate the viral genome
C) these enzymes translate viral mRNA into proteins
D) these enzymes penetrate host cell membranes

vi. 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

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

viii. A correct list of animals used for virus cultivation in the laboratory
A) guinea pig, chicken, mice and sheep B) monkey, goat, rabbit, rodent,
C) mice, rabbit, guinea pig and rat D) all of the above

ix. During viral inoculation in embryonated eggs which of the following is more important?
A) candling of eggs B) wiping of egg shell with spirit
C) drawing appropriate amount of inoculums D) punching of egg shell membrane

x. Viral growth and multiplication in the embryonated egg is indicated by———
A) death of the embryo B) haemorrhages of the embryo
C) edema and necrotic foci ‘pocks’ D) all the above

2. Indicate whether the following statements are true or false by writing TRUE for correct statement and FALSE for incorrect statement in the space provided (10 marks)
i. Viruses can be grown on any inanimate culture……………..
ii. Viruses can result in acute death of the host …………………
iii. Viruses can replicate in the cytoplasm and nucleus…………….
iv. The synthesis of viral proteins for all viruses is carried out in the cytoplasm using the host machinery……………………
v. Enveloped viruses acquire envelopes by generating it themselves during replication in the cell……………………
vi. Virus binding to the host cell requires the presence of specific ligands/spikes on the surface of the cell………………
vii. For enveloped viruses, assembly typically occurs at the site of replication…………….
viii. Viral replication steps are the best targets for the treatment of viral diseases using antivirals……………
ix. In HIV treatment most antiretrovirals target the reverse transcription step………………..
x. All DNA viruses replicate in the nucleus except poxvirus which replicate in the cytoplasm……………….

SECTION B (51 marks)
3. Write a word or phrase that best fits in the blank spaces below (11 marks)
i. In HIV replication, the integrated dsDNA into the host genome becomes permanent part of the host genome and is called……………………………………………. (3 marks)
ii. The form of a virus when is inside the cell is called…………………………. and when the virus is outside the cell is called……………… …………………………….. (2 marks)
iii. Virus replication cycle is also called………………… ……………… ……..(2 mark)
iv. The virus always will attach to the ………………………. present on the surface of cell using………………………………. present on the surface of the virus (2 marks)
v. Receptor-mediated endocytosis is one of the main mechanisms used by enveloped viruses to ……………………………………………………………………………………………..(2 marks)

4. Give the correct biological term for each of the following descriptions. Write only the term next to the question number (10 Marks)
i. A cell with the capacity to replicate the virus is called…………………………………….
ii. The process of bringing two separate membrane bilayers (viral envelope and plasma membrane) into intimate contact and then merging them into one……………………….
iii. The process whereby a virus capsid is completely or partially removed and the virus genome exposed………………………………………………………………………
iv. Viral proteins such as enzymes or transcription factors for virus replication which are not incorporated in the virus are called……………………………………………………….
v. The enzyme that MUST be packaged by -ssRNA viruses within their virion for replication and transcription………………………………………………………………..

 

6. Select the answer among the alternatives given in list B that best matches with the statement in list A, then write the letter of the correct response in spaces provided in list A. (10 marks)

LIST A

LIST B

i.   Replication of RNA viruses typically occurs in the………………   ii.      Replication of DNA viruses typically occurs in the…………….   iii.    The mechanism used by most of the non-enveloped viruses to leave the cell after replication………………………………..   iv.    In HIV replication, the cellular RNA polymerase II copies the …………. to make mRNA for viral proteins and full length viral RNAs   v.      The main route for inoculation of poxviruses in chicken embryonated eggs

A. Nucleus B. Golgi C. Endoplasmic reticulum D. Cytoplasm E. proviral RNA F. Budding G. viral DNA H. Allantoic route I.  Lysis J.  CAM

 

6. Differentiate the following terms as they are used in virology. Write your answer in one sentence only (20 marks)
a. A susceptible cell from a permissive cell (4 marks)
……………………………………………………………………………………………………………………………………………………………………………………………………………
b. A resistant cell from a susceptible cell (4 marks)
……………………………………………………………………………………………………………………………………………………………………………………………….
c. Virus attachment from virus fusion (4 marks)
……………………………………………………………………………………………………………………………………………………………………………………………………………
d. Virus internalization from virus uncoating (4 marks)
……………………………………………………………………………………………………………………………………………………………………………………………………………
e. Virus assembly from virus maturation (4 marks)
……………………………………………………………………………………………………………………………………………………………………………………………………………

SECTION C (19 marks)
7. List SEVEN parts/organelles that support the replication of viruses (7 marks)
a) …………………………………………… b)……………………………………………….
c) …………………………………………… d)………………………………………………..
e) …………………………………………… f)…………………………………………………
g)………………………………………………………………………………………………..
8. Mention THREE enzymes and ONE function for each that are packaged in the HIV virion for replication in the host cell (6 marks)
a)…………………………………………………………………………………………………
b)…………………………………………………………………………………………………
c)…………………………………………………………………………………………………
9. What are the SIX groups of Anti-HIV drugs (6 marks)
a)………………………………………. ……b)……………………………………………….
c) ……………………………………………….. d)……………… ………………………………. e)……………………………………………. f) ……………………………………………….

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