SOKOINE UNIVERSITY OF AGRICULTURE
VM 132: CAT FOR VIROLOGY PART
DEGREE PROGRAMME: BSc. ANIMAL SCIENCE
TIME ALLOWED: 1.5 HOURS DATE: 14-02-2021
Instructions:
1. This paper has FIVE printed pages with FIVE sections (A, B, C and D)
2. Answer ALL FIVE 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 (30 marks)
i. Which of the following is the correct set of acellular microorganisms?
A) viruses, protists, viroids and archea B) virusoids, prions, viruses and protists
C) viruses, prions, viroids and virusoids D) prions, bacteria, viruses and archea
ii. Viruses are referred to as obligate intracellular parasites because
A) viral DNA inserts itself into host DNA B) they use host energy to live
C) they replicate only in living susceptible cells D) they are non-living
iii. Viruses are made of
A) Protein coat, DNA B) Protein coat, RNA
C) Protein coat, DNA or RNA D) Protein coat, DNA and RNA
iv. One characteristic shared by a virus and a living cell is that both —
A) store genetic information in nucleic acids B) have a crystalline structure
C) gain energy directly from the sun D) use glucose for respiration
v. The host range of a virus is determined by
A) the enzymes carried by the virus B) whether its nucleic acid is DNA or RNA
C) the proteins in the host’s cytoplasm D) the enzymes produced by the virus
E) the proteins on the capsid and the proteins on host cell membranes
vi. Which of the following statements about viruses is false?
A) They come in many different shapes and sizes
B) They contain genetic material, protein and a few organelles
C) Each type of virus can only infect specific hosts
D) Different viruses infect hosts from all of the 5 kingdoms of life
vii. Viruses have some of the properties of living organisms. Which of the following is a characteristic of all organisms, but not of viruses?
A) plasma membrane B) ability to control metabolism
C) genetic information stored as nucleic acid D) structure includes proteins
E) ability to reproduce at fantastic rate
viii. Which of the following is a true statement about viruses?
A) A single virus particle contains both DNA and RNA
B) Viruses are classified below the cellular level of biological organization
C) Even small virus particles are visible with light microscopes
D) A and B only are true. E) A, B, and C are true
ix. A chemical component that is found in all viruses is:
A) Protein B) Lipid C) DNA D) RNA D) Glycoproteins
x. 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
xi. 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
xii. 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
xiii. 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
xiv. 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
xv. 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
SECTION B (20 Marks)
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 (1 mark each)
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……………….
xi. Viruses can be grown on any inanimate culture……………..
xii. Viruses can result in acute death of the host …………………
xiii. Viruses can replicate in the cytoplasm and nucleus…………….
xiv. The synthesis of viral proteins for all viruses is carried out in the cytoplasm using the host machinery……………………
xv. Enveloped viruses acquire envelopes by generating it themselves during replication in the cell……………………
xvi. Virus binding to the host cell requires the presence of specific ligands/spikes on the surface of the cell………………
xvii. For enveloped viruses, assembly typically occurs at the site of replication…………….
xviii. Viral replication steps are the best targets for the treatment of viral diseases using antivirals……………
xix. In HIV treatment most antiretrovirals target the reverse transcription step………………..
xx. All DNA viruses replicate in the nucleus except poxvirus which replicate in the cytoplasm……………….
SECTION C (20 marks)
3. Write a word or phrase that best fits in the blank spaces below
i. The internal part of a virus particle, which consists of the nucleic acid (either DNA or RNA never both) and closely associated proteins…………………………………. (2 marks)
ii. The outer shell of the virus which encloses the genetic material (composed of capsomers) is called………………………………………………………………………………(2 marks)
iii. In HIV replication, the integrated dsDNA into the host genome becomes permanent part of the host genome and is called……………………………………………. (2 marks)
iv. The form of a virus when is inside the cell is called…………………………. and when the virus is outside the cell is called……………… …………………………….. (2 marks)
v. The virus always will attach to the ………………………. present on the surface of cell using………………………………. present on the surface of the virus (2 marks)
vi. A cell with the capacity to replicate the virus is called……………………………………… (2 marks)
vii. The process of bringing two separate membrane bilayers (viral envelope and plasma membrane) into intimate contact and then merging them into one………………… (2 marks)
viii. The process whereby a virus capsid is completely or partially removed and the virus genome exposed……………………………………………………………………… (2 marks)
ix. Viral proteins such as enzymes or transcription factors for virus replication which are not incorporated in the virus are called………………………………………………… (2 marks)
x. The enzyme that MUST be packaged by -ssRNA viruses within their virion for replication and transcription……………………………………………………………….. (2 marks)
4. Complete the replication cycle of HIV by filling the gaps shown below (2 marks each = 22 total)
Replication cycle of HIV is the process to make new copies of the virus. The HIV virus only replicate in human cells called ……………………………… The HIV replication process carrying seven steps, the steps are entry, reverse transcription, integration, transcription, translation, assembly, release and maturation. This replication process starts with virus attaching on a special protein called …………………(found on the surface of the cell) by using………………….. (found on the surface of the virus). Then the viral and cellular membrane comes together and merge to form a single membrane, a process called……………… where viral genetic material are released into the cell. Once inside the cell, HIV converts its genetic material from RNA to ………………….by an enzyme called……………………………………………………… The converted genetic material then enters the nucleus where it is incorporated into the host genome by an enzyme known as……………………………………After incorporation, the viral genetic material is now referred to as …………………………………… Once the virus genome has become part of the host cell, it commands the cell to start transcribing it into RNA which are transported into the cytoplasm for making long single viral proteins. All the synthesized viral components come together with the HIV genome to form a new immature virus (noinfectious) in a process called………………………………………….. The synthesized long polyprotein needs to be cut up into separate functional proteins by an enzyme called ………………………………… creating the mature (infectious) virus. The newly formed HIV are released from the cell by a process called………………………………to infect other susceptible cells
5. 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 (1 mark each).
| LIST A | LIST B |
| i. Baltimore classification of viruses have………………groups
ii. Named based on how they were originally thought to be contracted………………………………………………….. iii. Tobacco mosaic virus, Ebora virus, influenza, measles and rabies virus are examples of viruses with ……………….. capsid symmetry iv. Viruses originated from cellular (RNA and DNA) genetic material that has acquired the capacity to exist and function independently……………………………………………………………. v. Replication of RNA viruses typically occurs in the……………… vi. Replication of DNA viruses typically occurs in the……………. vii. The mechanism used by most of the non-enveloped viruses to leave the cell after replication……………………………….. viii. In HIV replication, the cellular RNA polymerase II copies the …………. to make mRNA for viral proteins and full length viral RNAs
|
A. Six groups
B. Seven groups C. Bunyaviruses D. Dengue virus E. RNA viruses F. DNA viruses G. Icosahedral H. Helical I. Reduction hypothesis J. Escape hypothesis K. Nucleus L. Ribosomes M. Cytoplasm N. Budding O. Lysis P. Proviral RNA Q. Proviral DNA |
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