Viral Agents and Structure (2,3,4) Flashcards

1
Q

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

A

c. The compounds should be highly soluble

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2
Q

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

A

b. A negative stain must be applied first

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3
Q

The following does not have icosahedral capsid symmetry:

a. Herpesvirus
b. Papillomavirus
c. Adenovirus
d. Retrovirus

A

d. Retrovirus

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4
Q

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

a. It can possess either icosahedral or helical capsid symmetry depending on the species

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5
Q

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

A

b. The size of the genome and differences in sequence can distinguish a genus from other genera

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6
Q

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

A

c. ssRNA forms a precipitate when exposed to TCA

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7
Q

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

A

d. It encodes RNA polymerase

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8
Q

• X ray diffraction can only be used on non-enveloped viruses.

A

T

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9
Q

• In a viral envelope, the phospholipids are virus-encoded whilst the glycoproteins and host encoded.

A

F

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10
Q

• Icosahedral capsid symmetry is only found in enveloped viruses.

A

F

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11
Q

• Enveloped viruses are less stable than naked viruses.

A

T

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12
Q

• 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.

A

T

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13
Q

• When extracting NA from viruses and cells, the upper aqueous phase contains protein and the lower phenol phase contains nucleic acids.

A

F

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14
Q

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

A

b. CSF for encephalitis

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15
Q

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

a. Chorioallantoic membrane

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16
Q

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

A

d. All modern vaccines are cultivated using continuous cell lines

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17
Q

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

A

b. It involves the loss of all nuclei in a cell

18
Q

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

A

d. It is a quick method and the gold standard for diagnosing viral infection

19
Q

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

A

b. RT-PCR for viral RNA

20
Q

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

a. It requires a single stranded DNA sample

21
Q

• Direct visualisation by EM is the fold standard required to study a virus.

A

F

22
Q

• Virus cultures are always handled in PC4 conditions.

A

F

23
Q

• Nuclear inclusions are usually caused by DNA viruses whilst cytoplasmic inclusions are usually caused by RNA viruses.

A

T

24
Q

• Antigen capture assays are highly sensitive whilst anti-viral antibody assays are highly specific.

A

T

25
Q

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

A

c. Unit which makes up the capsid or nucleocapsid

26
Q

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

A

d. Target cells act as a trigger for virions to disassemble

27
Q

Which best describes density gradient centrifugation?

a. Rate zonal density gradient centrifugation depends on the size and density 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

a. Rate zonal density gradient centrifugation depends on the size and density of a particle

28
Q

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

A

b. Smaller protein mass correlates to a higher intensity stained band

29
Q

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

A

d. SDS gels show that the virus has four viral proteins not present in equimolar amounts

30
Q

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

a. Left, right or central helix

31
Q

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 comples

A

b. It is found exclusively in the nucleus

32
Q

• The steps (in order) for chemical purification of a virus are cell disruption, centrifugation and density gradient centrifugation.

A

T

33
Q

• Non-ionic detergents are best used to disrupt viruses found in the nucleus.

A

F

34
Q

• Low speed centrifugation results in small organelles, ribosomes and viruses pelleting.

A

F

35
Q

• High speed centrifugation results in virus particles being found in the pellet and the supernatant can be discarded.

A

T

36
Q

• The virion structure is not permanently bonded together in order for the viral genome to be exposed or released.

A

T

37
Q

• Adenovirus contains a similar amount of proteins to Poliovirus and these are present in equimolar amounts.

A

F

38
Q

• Papillomavirus has 72 capsomers which are all hexons as expected.

A

F

39
Q

• The genome is a viral structural component and present in purified virions.

A

T

40
Q

• Non-structural viral proteins can be found in infected cells but not uninfected cells.

A

T