MST1 L2-10 Questions Flashcards
What is required for negative staining?
a. Compounds should be proton dense
b. The compounds should be able to crystallise
c. The compounds should be highly soluble
d. Calcium phosphotungstate
c. The compounds should be highly soluble
What is false about cryo-electron microscopy?
a. The sample is not distorted and allows the structure to be analysed
b. A negative stain must be applied first
c. Different 2D views can be reconstructed to form a 3D structure
d. A computer can be used to reconstruct the image of the virus
b. A negative stain must be applied first
What is the name for each component described?
Protective protein shell. Surrounds genome, forms core of particle. Clusters of subunits called capsomers
The proteins closely assembled with viral nucleic acid
Lipoprotein membrane. Surround capsid or nucleocapsid. Phospholipids from host PM, glycoproteins virus encoded
Protein layer under envelope. Connects capsid and envelope glycoproteins.
Capsid
Nucleocapsid
Envelope
Matrix
The following does not have icosahedral capsid symmetry:
a. Herpesvirus
b. Papillomavirus
c. Adenovirus
d. Paramyxovirus
d. Paramyxovirus
What is false about Poxvirus?
a. It can possess either icosahedral or helical capsid symmetry depending on the species
b. It is the largest and most complex virus
c. IT has over 100 proteins in the virion
d. It has a 130-280 kb dsDNA genome
a. It can possess either icosahedral or helical capsid symmetry depending on the species
What is true about classifying viruses according to family and genus?
a. Family names end in virus and genus names end in viridae
b. The size of the genome and differences in sequence can distinguish a genus from other genera
c. The number and size of proteins is used to classify families
d. Viral replication strategies and morphology are used to distinguish between genera
b. The size of the genome and differences in sequence can distinguish a genus from other genera
What is false about determining if a virus has ssRNA or dsRNA?
a. RNase only digests ssRNA
b. TCA precipitates radioactive RNA polymers and the presence of precipitate demonstrates undigested RNA (double stranded)
c. ssRNA forms a precipitate when exposed to TCA
d. ssRNA would produce free uracil nucleotides when exposed to RNase and these remain in solution after treatment with TCA
c. ssRNA forms a precipitate when exposed to TCA
What is the order of modified Koch’s postulates?
• Virus reisolated from experimentally infected animal
• Clinical syndrome reproducible in volunteers/animals
• Virus characterised. Isolated via animal/cell0culture passage and distinguished from other viruses immunologically or genetically
• Virus associated with clinical disease
- Virus associated with clinical disease
- Virus characterised. Isolated via animal/cell0culture passage and distinguished from other viruses immunologically or genetically
- Clinical syndrome reproducible in volunteers/animals
- Virus reisolated from experimentally infected animal
What is false about Hepatitis D?
a. It is a covalently closed circular RNA viroid element
b. It is dependent on hepatitis B for transmission and acts as a parasite of a virus
c. It can be considered an emerging infectious agent
d. It encodes RNA polymerase
d. It encodes RNA polymerase
• X ray diffraction can only be used on non-enveloped viruses.
T
• In a viral envelope, the phospholipids are virus-encoded whilst the glycoproteins and host encoded.
F
• Icosahedral capsid symmetry is only found in enveloped viruses.
F
• Enveloped viruses are less stable than naked viruses.
T
• Purified virions containing H suggest that the virus has an RNA genome whilst purified virions containing C suggest that the virus has a DNA genome.
T
• When extracting NA from viruses and cells, the upper aqueous phase contains protein and the lower phenol phase contains nucleic acids.
F
What sample would be taken to identify a virus from the following infections?
a. A faecal sample for a systemic fever
b. CSF for encephalitis
c. Nasal secretions for a vesicular rash
d. Blood for an enteric infection
b. CSF for encephalitis
What part of an embryonated chicken egg would be used to cultivate Poxvirus?
a. Chorioallantoic membrane
b. Yolk sac
c. Amniotic fluid
d. Allantoic fluid
a. Chorioallantoic membrane
What is false about mammalian cell culture methods?
a. Primary cells can only survive up to 10 divisions
b. Continuous cell lines are aneuploid
c. Diploid cell lines can survive up to 100 divisions
d. All modern vaccines are cultivated using continuous cell lines
d. All modern vaccines are cultivated using continuous cell lines
What is false about syncytia?
a. It can be a result of measles virus
b. It involves the loss of all nuclei in a cell
c. It occurs during virus replication when neighbouring cells may fuse
d. Viral fusion proteins expressed on host membranes aid syncytia
b. It involves the loss of all nuclei in a cell
What is false about infectivity/serology assays?
a. Detecting viral antigens is highly sensitive and can yield false positives
b. Anti-viral antibodies in patient serum can be detected using western blot
c. Detecting host antibodies is highly specific and can yield false negatives
d. It is a quick method and the gold standard for diagnosing viral infection
d. It is a quick method and the gold standard for diagnosing viral infection
How might viral nucleic acid be detected?
a. A southern blot for viral RNA
b. RT-PCR for viral RNA
c. A northern blot for viral DNA
d. Whole genome sequencing
b. RT-PCR for viral RNA
What is not a feature of PCR?
a. It requires a single stranded DNA sample
b. It is very specific and sensitive
c. Contamination can easily occur
d. It is cheap and automated
a. It requires a single stranded DNA sample
• Direct visualisation by EM is the gold standard required to study a virus.
F
• Virus cultures are always handled in PC4 conditions.
F
• Nuclear inclusions are usually caused by DNA viruses whilst cytoplasmic inclusions are usually caused by RNA viruses.
T
• Antigen capture assays are highly sensitive whilst anti-viral antibody assays are highly specific.
T
What describes a structural unit?
a. The infectious viral particle
b. The nucleic acid-protein assembly within a virion
c. Unit which makes up the capsid or nucleocapsid
d. Single folded polypeptide chain
c. Unit which makes up the capsid or nucleocapsid
In what ways are virions metastable?
a. Virions do not have moving parts
b. Viral particles have reached the minimum free energy conformation
c. Virions are always stable so that they can protect the genome
d. Target cells act as a trigger for virions to disassemble
d. Target cells act as a trigger for virions to disassemble
Which best describes density gradient centrifugation?
a. Rate zonal density gradient centrifugation depends on the size and mass of a particle
b. Equilibrium density gradient centrifugation depends on the density, mass and sedimentation coefficient of a particle
c. Equilibrium density gradient centrifugation requires a pre-formed gradient and can be completed in a few hours
d. Rate zonal density gradient centrifugation uses a high density solution and takes many hours to complete
a. Rate zonal density gradient centrifugation depends on the size and mass of a particle
What is false about SDS gel electrophoresis?
a. SDS is anionic and binds to proteins after disrupting the virion
b. Smaller protein mass correlates to a higher intensity stained band
c. Proteins move to the cathode according to their molecular weight
d. Equimolar proteins contain the same number of molecules
b. Smaller protein mass correlates to a higher intensity stained band
What is not a feature of poliovirus?
a. It is part if the Picornaviridae family and has a +ssRNA genome
b. It has tiny viral particles with an icosahedral structure
c. The virus has 60 capsomers and each has one copy of four viral proteins
d. SDS gels show that the virus has four viral proteins not present in equimolar amounts
d. SDS gels show that the virus has four viral proteins not present in equimolar amounts
Which feature is not used to distinguish helical capsids?
a. Left, right or central helix
b. Number of nucleocapsids per turn
c. Axial rise per subunit
d. Pitch per turn
a. Left, right or central helix (no central)
What is not a feature of the Measles virus nucleoprotein?
a. It is 60kDa and has 525 amino acids
b. It is found exclusively in the nucleus
c. It is abundant in infected cells and self assembles to form the nucleocapsid
d. It can form a ribonucleoprotein complex
b. It is found exclusively in the nucleus
• The steps (in order) for chemical purification of a virus are cell disruption, centrifugation and density gradient centrifugation.
T
• Non-ionic detergents are best used to disrupt viruses found in the nucleus.
F
• Low speed centrifugation results in small organelles, ribosomes and viruses pelleting.
F
• High speed centrifugation results in virus particles being found in the pellet and the supernatant can be discarded.
T
• The virion structure is not permanently bonded together in order for the viral genome to be exposed or released.
T
• Adenovirus contains a similar amount of proteins to Poliovirus and these are present in equimolar amounts.
F
• Papillomavirus has 72 capsomers which are all hexons as expected.
F
• The genome is a viral structural component and present in purified virions.
T
• Non-structural viral proteins can be found in infected cells but not uninfected cells.
T
How is the growth curve different between enveloped and non-enveloped viruses?
a. Non-enveloped viruses do not demonstrate a latent period
b. Enveloped viruses have a higher yield when they are intracellular
c. Intracellular viruses have a higher yield when non-enveloped and extracellular viruses have a higher yield when enveloped
d. The uncoating phase is only seen in enveloped viruses and has a low gradient on the curve
c. Intracellular viruses have a higher yield when non-enveloped and extracellular viruses have a higher yield when enveloped
What does it mean if P(0) = 0.02?
a. The multiplicity of infection is at 2%
b. 2% of cells are not infected
c. There is a 2% chance that any cell will become infected
d. There are 2 plaque forming units/cell
b. 2% of cells are not infected
What is not a method used by viruses to invade host cells?
a. Fusion and direct uncoating at the plasma membrane
b. Pinocytosis or phagocytosis
c. Endocytosis followed by uncoating within the endosome
d. Endocytosis followed by uncoating at the nuclear membrane
b. Pinocytosis or phagocytosis
What is not involved in the entry and uncoating of adenovirus?
a. The virus directly fuses with the host cell using CAR receptors and uncoats at the cell surface
b. When the endosome acidifies, the penton base is released and bursts the endosome so the capsid can be released
c. The adenovirus penton fibre interacts with intergrins recpetors called CAR to initiate RME
d. Once the capsid is released from the endosome, it travels to the nuclear pore using the host cell microtubule network
a. The virus directly fuses with the host cell using CAR receptors and uncoats at the cell surface
What is not involved in the entry and uncoating of Reovirus?
a. The capsid undergoes proteolysis in the endosome to produce the infectious subviral particle (ISVP)
b. ISVP proteins prevent endosome maturation and the virus can persist in the host
c. The outer capsid proteins bind cell receptors to mediate RME
d. ISVP proteins mediate membrane penetration
b. ISVP proteins prevent endosome maturation and the virus can persist in the host
What does not occur during entry of Influenza?
a. Envelope haemagglutinin molecules bind sialic acid on cell glycoproteins
b. Neuraminidase releases sialic acid and is part of the viral envelope
c. Endosome acidification is required so that the fusion domain of haemagluttinin can be exposed
d. The virus enters host cells by interacting with glycoprotein sialic acid and directly fusing with the plasma membrane
d. The virus enters host cells by interacting with glycoprotein sialic acid and directly fusing with the plasma membrane
What is CD46/SLAM?
a. A paramyxovirus ligand that reacts initiates fusion of the measles virus
b. A HIV-1 ligand that interacts with CD4 co-receptors during cell entry
c. The product of VP4 in Rotavirus following cleavage by trypsin
d. The flavivirus peptide that initiates membrane fusion following conformational change
a. A paramyxovirus ligand that reacts initiates fusion of the measles virus
What is the correct description for HIV-1 glycoproteins?
a. Gp120, gp41 and gp160 all exist as a trimer
b. Only gp160 can bind CD4
c. Gp160 is the precursor for gp41 and gp120
d. Gp41 is a surface protein and gp120 is a transmembrane protein
c. Gp160 is the precursor for gp41 and gp120
What happens during HIV entry? (put in order)
• Binding of gp120 to CCR causes conformational change in gp41 (transmembrane) and fusion peptide is inserted into membrane
• Gp120 (surface) binding to CD4 causes conformational change in gp120. Exposes binding site for chemokine coreceptor (CCR)
• HIV-1 envelope glycoproteins gp120-41 bind CD4
- HIV-1 envelope glycoproteins gp120-41 bind CD4
- Gp120 (surface) binding to CD4 causes conformational change in gp120. Exposes binding site for chemokine coreceptor (CCR)
- Binding of gp120 to CCR causes conformational change in gp41 (transmembrane) and fusion peptide is inserted into membrane
What is used to determine is a virus infects a cell via endocytosis or direct fusion?
a. Genome sequencing and analysis
b. Exposing cells to a weak base to prevent endosome acidification
c. Electron microscopy
d. PCR for well-known fusion proteins such as SLAM, Gp120 and Gp41
b. Exposing cells to a weak base to prevent endosome acidification
• Initial binding of a virus is specific and the strongest form of attachment due to covalent protein-protein interactions.
F
• Virions may enter a cell by fusion, receptor mediated endocytosis or passive pinocystosis.
F (not pino)
• Measles virus unocats by fusing their envelope with the cell plasma membrane.
T
• Poliovirus enters a cell after interaction between the CD155 receptor and capsid leads to a conformational change of the VP1 capsid protein.
T
• All reoviruses have a double shelled capsid except for rotavirus.
F
• It is common for enveloped viruses to enter in the endosome and rely on endosome acidification initiating a conformational change.
T
What kind of viruses can directly fit into the flow of cell genetic information and can use cell enzymes?
a. dsDNA virsues and ss +RNA genome viruses
b. ss-RNA viruses
c. ss-RNA viruses and ss+ RNA viruses
d. ssDNA viruses and ds linear DNA viruses
a. dsDNA virsues and ss +RNA genome viruses
What is involved in cellular transcription?
a. RNA pol II binds downstream of the promoter
b. Transcription initiation factors bind the core promoter or enhancer sequences
c. RNA pol II is recruited directly by the enhancer
d. mRNA is synthesised from a DNA template using dNTPs
b. Transcription initiation factors bind the core promoter or enhancer sequences
Which DNA viruses carry their own polymerase?
a. Adenovirus and Papovavirus
b. Poxvirus and Herpesvirus
c. Adenovirus and Herpesvirus
d. Hepadnavirus and Poxvirus
d. Hepadnavirus and Poxvirus
What is false about transcriptional regulation in Papovavirus SV40?
a. VP2 and VP3 genes overlap and share some AAs due to being in the same reading frame
b. Early genes are transcribed in a counter clockwise direction and late genes are transcribed in a clockwise direction
c. Early promoters are recognised by host cell RNA transcription factors
d. The large T protein is produced following transcription of late genes
d. The large T protein is produced following transcription of late genes