BLS 113_CAT 2_2023

SOKOINE UNIVERSITY OF AGRICULTURE
College of Veterinary Medicine and Biomedical Sciences

BLS 113: Virology CAT 2 Total Marks: 62 Date: 9th June 2023 Time: 40 minutes

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

i. Which viruses appear to be hypermutable?
A) DNA viruses B) ‘Emerging’ viruses C) Influenza and HIV D) RNA viruses

ii. Which of the following are necessary for viral reassortment to occur?
A) a circular viral genome
B) a segmented viral genome
C) an ambisense viral genome D) provirus

iii. The following routes that can serve for both entry into the host and shedding of the virus to the environment
A) Mouth, anus and conjunctiva
B) Anus, urogenital and respiratory tract
C) Mouth, urogenital tract and conjunctiva
D) Mouth, skin and respiratory tract
E) Skin, urogenital and respiratory tract

iv. In phenotypic mixing, two virus particles share
A) Envelope B) Coat proteins
C). Genetic material D) Nucleocapsids
E). Segments

v. The following are DNA viruses (circle all that apply)
A) Herpesviruses B) Orthomyxoviruses
C). Enteroviruses D) Hepadnaviruses
E). Parvoviruses

vi. The following are RNA viruses (circle all that apply)
A) Picornaviruses B) Adenoviruse
C). Papillomaviruses D) Rhabdoviruses
E). Rotaviruses

vii. Inclusion bodies of rabies virus are called:
A) intracytoplasmic B) intranuclear
C) Negri bodies C) both (a) and (b)
D) none of the above

viii. Mutations in viral genomes… (circle all that apply)
A) can cause phenotype changes in the virus
B) can be missense mutations
C) occur more frequently in RNA viruses
D) can be nonsense mutations
E) can be increased by the presence of certain chemicals

ix. The vast majority of viruses encountered by the host…
A) can be mitigated by the host immune system
B) are responsible for about 90% of all morbidity and mortality
C) are lethal
D) have the ability to overcome the host immune system
E) make human and animals sick

x. Influenza A Virus (circle all that apply)
A) May undergo antigenic shift and antigenic drift
B) May cause pandemics
C) Respond to rimantidine
D) Respond to neuraminidase inhibitors
E) Vaccination confers lifelong protection

xi. Which of the antiviral agents match against their respective target virus replication step (circle all that apply)
A) Amantadine and uncoating
B) Maraviroc and protease inhibitors
C) Acyclovir and nucleic acid synthesis
D) Enfuvirtide and fusion

xii. HIV may respond to (circle all that apply)
A) Nucleoside analogues
B) Protease inhibitors
C) Neuraminidase inhibitors
D) Reverse transcriptase inhibitors
E) Acyclovir

xiii. Agents that interfere with viral multiplication include (circle all that apply)
A) Amphoteriein B
B) Amantadine
C) Metronidazole
D) Zidovudine
E) Ribavirin

xiv. During the incubation period of HIV infection, there is (circle all that apply)
A) Little HIV replication
B) HIV is mainly integrated into the genome of long-lived cell populations
C) High turnover of CD4 cells
D) The viral load has a direct bearing on the prognosis
E) Little antibody against the HIV envelope

xv. The viruses in an attenuated vaccine
A) have no genome
B) have no capsid
C) continue to replicate
D) are usually larger than bacteria
E) is altered with chemicals

xvi. Enzyme hemagglutinin is carried by which of the following viruses?
A) Human immunodeficiency virus
B) Epstein-Barr virus
C) Influenza virus
D) Adenovirus

xvii. Which one is not useful in the treatment of viruses
A) Acyclovir
B) Interferon
C) Penicillin
D) Antibodies

xviii. The infected cells continue to reproduce themselves as well as the virus, and the mature virions are extruded from the cell surface continuously over a long period of time. This type of release mechanism is called a
A) productive infection
B) inductive infection
C) resultant infection
D) all of these

xix. Intracellular structures formed during many viral infections, called __________, which can directly disrupt cell structure.
A) prokaryotes
B) chromosomal disruptions
C) inclusion bodies
D) cytocidal bodies

xx. Influenza virus undergoes antigenic shift resulting in major antigenic changes by which of the following mechanisms?
A) Somatic recombination of heavy and light chains
B) Expression of several different capsule types
C) Changing the receptor binding canyon that docks with the host receptor
D) Reassortment of RNA segments from different influenza viruses

2. The figure below represents a single-cell replication cycle of a simple retrovirus (answer using the back of this page)
i. Name all the steps labelled 1 to 16 that forms a complete replication cycle of retroviruses (32 marks)
ii. What are the three important enzymes that are involved in this replication cycle (3 marks)
iii. Provide one function of enzyme named in “ii” above (6 marks)
iv. Provide one example of the virus that belong to genus retrovirus (1 marks)

 

**************************BEST WISHES*******************************