Week 2&3 Questions Flashcards
MCQ1: How do virus attachment proteins find receptors to attach onto?
- Sensing receptors are near by
- Colliding with cells via Brownian Motion
T/F Question 1: Receptors for dengue virus in host cells include heparan sulfate molecules.
True - present in almost all cells
T/F Question 2: A mode of virus entry into the host cell that is shared between enveloped and non-enveloped viruses is fusion at the cell membrane.
False - only enveloped viruses sometimes use diffusion
MCMO 1: Which of the following are necessary for dengue virus entry via endocytosis to occur successfully?
a) Fusion at the host cell membrane between virus and cell
b) Uncoating of the capsid
c) Formation of an endosome
d) Lowering of the pH in the endosome
c) Formation of an endosome
d) Lowering of the pH in the endosome
MCQ 2: For an enveloped virus that undergoes membrane fusion, the envelope is:
a) Brought into the endosome
b) Left behind in the cytoplasm
c) Left outside the cell
d) Travels to the nucleus if the virus is a DNA virus
e) Destroyed in the cytoplasm by host enzymes
c) Left outside the cell
Complete the sentence: Capsid softening occurs when acidification of the endosome triggers ____ leading to ____________________
Due to the lowering of the pressure inside, conformational changes occur allowing the release of the nucleic acid.
SAQ 1: The entire lifecycle of most RNA viruses takes place in the host cell cytoplasm. However, Influenza has one key difference. Explain what this.
It replicates in the nucleus.
Does this because of genetic re-assortment (when two viruses can meet and become a new one)
T/F Question 3: DNA viruses always need to bring along their own replicative enzymes otherwise their lifecycle cannot be completed.
False - Most DNA viruses use the hosts cell’s DNA polymerase
SAQ 2: The Baltimore scheme of virus classification has one type of virus genome and replication strategy missing. What is it?
No negative sense single stranded DNA virus.
- Doesn’t exist as DNA can only replicate in one direction
MCQ 3: Cytomegalovirus (CMV) belongs to which class of viruses in the Baltimore scheme?
a) Class III
b) Class IV
c) Class V
d) Class VII
e) Class I
Class I (dsDNA)
CMV = type of Herpesvirus
Varicella-Zoster Virus (VZV) = Herpesvirus
What baltimore class is Herpesvirus?
Class I - Double Stranded DNA (dsDNA)
What baltimore class is SARS-CoV-2
Class IV - Single Stranded RNA genome
Name the Baltimore Classifications? (Hint there are 7)
Class I - dsDNA
Class II - ssDNAn
Class III - dsRNA
Class IV - ssRNA +
Class V - ssRNA -
Class VI - ssRNA - RT
Class VII - dsRNA -RT
What Baltimore classification is HIV?
Class VI (ssRNA +)
MCQ 4: Which class of viruses is most similar to how transcription, replication and translation occur in animal cells (Eukaryotes)?
a) Class III
b) Class IV
c) Class V
d) Class VII
e) Class I
Class I (dsDNA)
As double stranded and undergoes similair replicate
In the Baltimore classification, what class is parvovirus?
Class II (sdDNA)
SAQ 3: Human papilloma virus (HPV) is a DNA virus that is known to cause tumours. Which Baltimore class does it belong to? What key event occurs during infection with this virus compared to other viruses in its Baltimore class? How does it promote tumour formation?
Class I virus
- Integrates into the genome (changing it)
- Transcription of the genes, upregulates viral oncogenes (viral proteins) to upregulate cell signaling cascades.
SAQ5: What do parvoviruses (Class II in the Baltimore scheme) need to do first in order for translation to occur and why?
Needs to transcribe the minus strand, for the RNA to translate into a viral protein.
Anti-genome needs to form DNA intermediate (a temporary double stranded DNA used for mRNA)
For understanding
- Parvoviruses start with a single-stranded DNA genome.
- They need to convert this into double-stranded DNA because cells can only make mRNA from double-stranded DNA.
- The cell uses one strand of this double-stranded DNA (intermediated DNA) to make mRNA.
-The mRNA is then used by the cell to make the viral proteins.
SAQ 6: What key feature is different between class VII (Hepatitis B) and Class I viruses?
(Be able to draw diagram for exam)
- Class IIV is reverse transcription, this RNA gets encapsulated (as RNA isn’t naturally in the cytoplasm)
- Has an intermediated RNA
- Class I can be transcribed straight into mRNA
MCMO 2: Which of the class/ classes of viruses below do NOT need to bring along in their virions the RNA dependent RNA polymerase (RdRp or RNA replicase)?
a) Class I
b) Class III
c) Class IV
d) Class V
e) Class VI
Class IV, VI
Explanation:
RdRp - only refers to RNA (not DNA)
+ RNA can use hosts (therefore they don’t carry)
MCQ 5: Why is the Rotavirus genome never completely uncoated from its capsid?
a) It is needed for maturation of new viral particles
b) It protects the single stranded RNA genome
c) It protects the double stranded RNA genome
d) It catalyses the formation of new capsids
(Note: Rotavirus is class VI ssRNA - RT)
c.) It protects the double stranded RNA gecnome
- Prevent damage and protection
- RNA is more chemically reactive (capsulate it)
SAQ 7: What is special about Class 4 viruses such as dengue?
Class IV (ssRNA plus sense)
- translated directly into protein
- positive sense acts as template mRNA
- Makes an entire polyprotein or two poly-proteins (cut up by protease)
MCQ 5: How many polyproteins are translated in Ross River virus?
a) One
b) Two
c) Three
d) Four
e) Nine
(Class VI)
b.) two
T/F: In SARS-CoV-2, the structural proteins are translated at the same time as the non-structural proteins directly off the genome which acts as a mRNA.
False:
Step 1: enters host cell, makes polyprotein using non-structural proteins.
Step 2: Synthesis then use of structural proteins.
