SOKOINE UNIVERSITY OF AGRICULTURE
College of Veterinary Medicine and Biomedical Sciences
BLS 113: Virology CAT 1 Total Marks: 100 Date: 28th March 2024 Time: 1 hour
General instructions: Answer all THREE questions. A zero mark will be given to any rubbed or cancelled answer in the specific question.
1. Select the best answer among the alternative statements given for each question and circle it (60 marks)
i. A chemical component that is found in all viruses is:
A) Protein B) Lipid C) DNA D) RNA E) Carbohydrate
ii. A structural component that is found in all viruses is:
A) The envelope B) DNA C) Capsid D) Tail fibers E) Matrix core
iii. Which of the following is not true of virions?
A) Reproduce independently B) Contain DNA C) Contain RNA D) Are extracellular
iv. A common polyhedral capsid shape of viruses is a:
A) Pentagon B) Cube C) Icosahedron D) Pyramid E) Sphere
v. The viral nucleocapsid is the combination of
A) genome and capsid B) capsid and spikes C) envelope and capsid D) capsomere and genome
vi. In the simplest capsid, there is a capsomere at each of the 12 vertices; this capsomere, which is surrounded by five other capsomeres, is termed a
A) penton B) polyhedral C) icosahedral D) helical
vii. Poxviruses replicate:
A) On a plasmid B) In the cytoplasm C) Nucleus D) Within the nucleus
viii. Replication of RNA viruses typically occurs in the:
A) Nucleus B) Golgi C) Endoplasmic reticulum D) Cytoplasm
ix. Which of the following internalization method is mostly used by enveloped viruses to enter a cell:
A) fusion B) viropexis C) integration D) pore formation
x. Which viruses always have an RNA genome that acts as a template for DNA synthesis?
A) reoviruses B) retroviruses C) hepadnaviruses D) influenza A virus
xi. Viruses largely lack metabolic machinery of their own to generate energy or to synthesize….
A) protein B) carbohydrate C) capsid D) nucleic acids
xii. When a virus enters a cell but does not replicate immediately, the situation is called
A) lysogeny B) latent C) symbiosis D) synergism E) incubation F) lytic
xiii. The first step in infection of a host cells by a virus is called
A) adsorption B) absorption C) abruption D) penetration E) replication F) fusion
xiv. In the one-step growth curve, the time from infection until lysis is known as
A) eclipse period B) rise period C) latent period D) burst size
xv. All negative sense RNA viruses have:
A) no envelope B) envelope C) segmented genomes only D) non-segmented genomes only
E) no RNA-dependent RNA polymerase
xvi. Which of the following is the correct set of acellular microorganisms?
A) viruses, protists, viroids and archaea B) virusoids, prions, viruses and protists
C) viruses, prions, viroids and virusoids D) prions, bacteria, viruses and archaea
xvii. Viruses are referred to as obligate intracellular parasites because
A) viral DNA inserts itself into host DNA B) they reproduce and then exit the cell.
C) they are non-living D) they use the host’s energy to live.
E) they use the host cell’s nucleotides and enzymes to reproduce.
xviii. 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 before it infects the cell
E) the proteins on the capsid and the proteins on host cell membranes
xix. 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
xx. What is the most important factor for virus classification?
A) The geometry of the virus B) How many proteins the virus has
C) The disease a virus causes D) Chemistry of the DNA and RNA
xxi. Positive stranded RNA viruses have which of the following characteristics?
A) Their genome RNA can be translated directly as mRNA
B) They have to transcribe their genome RNA to a mirror image copy as a mRNA
C) This genome is circular
D) Their RNA genome is segmented
xxii. Viruses that contain two complete copies of positive strand RNA and the enzyme reverse transcriptase are:
A) Toga viruses B) Rhabdoviruses
C) Retroviruses D) Reoviruses E) Enteroviruses
xxiii. Certain virus has an enzyme called “RNA-dependent RNA polymerase” packed inside its capsid (along with the virus’ genome). This virus…
A) Is a retrovirus
B) Makes a DNA copy of its RNA genome and inserts the cDNA into the host cell genome C) Has a DNA genome
D) Transcribes mRNA from its RNA genome
E) Relies on the host cell to transcribe its genes into mRNA
xxiv. Which Influenza Envelope proteins facilitate binding to host cells and fusion
A) Hemagglutinin (H) B) Neuraminidase (N) C) M2
xxv. According to the Baltimore Classification Scheme of Viruses, SARS CoV-2 belongs to which group?
A) single stranded positive DNA genome B) single stranded positive RNA genome
C) single stranded negative RNA genome D) single stranded positive DNA genome
xxvi. Which of the statements below is false regarding virology?
A) Viral particles are utilized to transfer viral genomes between hosts
B) Viral genomes establish themselves in a host
C) Viruses contain their own functional ribosomes
D) Viral genomes are obligate molecular parasites
xxvii. How do enveloped viruses acquire their envelope?
A) Directly from the host cell membrane B) Through the Golgi apparatus
C) From the endoplasmic reticulum C) During replication inside the host nucleus
xxviii. What is the function of viral spikes or glycoproteins?
A) Protect the virus from host immune responses B) Aid in viral attachment to host cells
C) Facilitate viral replication D) Store genetic material
xxix. In positive-sense RNA viruses, the genome can be directly translated into proteins by host ribosomes. What does “positive-sense” mean in this context?
A) The RNA strand is complementary to mRNA B) The RNA strand serves as mRNA
C) The RNA strand lacks protein-coding information D) The RNA strand is double-stranded
xxx. Which of the choices below represents a chronological order for a virus recognizing a cell and initiating a viral infectious cycle?
A) Virus attachment, viral genome release, virion assembly, viral protein synthesis
B) Virus attachment, virion assembly, viral protein synthesis, viral genome release
C) Virus attachment, virion assembly, viral genome release, viral protein synthesis
D) Virus attachment, viral genome release, viral protein synthesis, virion assembly
2. Match list A with the correct answer in list B, then write the letter from list B in spaces provided in list A (30 marks)
| LIST A | LIST B |
| i. Named based on how they were originally thought to be contracted………..
ii. Tobacco mosaic virus, Ebora virus, influenza, measles and rabies virus are examples of viruses with ……………….. capsid symmetry iii. Viruses originated from cellular (RNA and DNA) genetic material that has acquired the capacity to exist and function independently……………………… iv. Example of a virus with the nature of the symmetry not fully understood giving an appearance of untidy ball of wool………………………………………. v. A form of a virus when outside the cell…………………………………….. vi. The mechanism used by most of the non-enveloped viruses to leave the cell after replication………………………………………………………… vii. A process where viral envelope merges directly with the host cell membrane……………………………………………………………………. viii. A process of internalization where a viral particle is engulfed by the host cell membrane……………………………………………………………….. ix. The enzyme that MUST be packaged by -ssRNA viruses within their virion for replication and transcription…………………………………………….. x. An enzyme that synthesizes DNA from RNA template of viruses………… xi. An enzyme that synthesizes RNA during RNA virus replication…………. xii. Viruses with genome complementary to mRNA synthesis………………….. xiii. Viral proteins such as enzymes or transcription factors for virus replication which are not incorporated in the virus are called…………………………………… xiv. A cell with the capacity to replicate the virus is called……………………… xv. The integrated retroviral DNA genome is called………………………….. |
A. Regressive theory
B. DNA polymerase C. Icosahedral D. Poxvirus E. Dengue virus F. Progressive theory G. Helical H. Permissive I. Virus fusion J. -ssRNA viruses K. RdDp L. Provirus M. Non-structural proteins N. +ssRNA viruses O. Lysis P. Endocytosis Q. Susceptible R. Core S. Proviral RNA T. Reverse transcriptase U. RNA polymerase V. Prion W. RdRp X. Virion Y. Budding |
3. Veropexis is the most common cellular entry technique for viruses. What are the FIVE (5) important viral entry pathways under this technique (10 marks)
a) ———————————————————————————————
b) ———————————————————————————————
c) ———————————————————————————————
d) ———————————————————————————————
e) ———————————————————————————————
***************************BEST WISHES****************************************