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Virology > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

The purpose of the life cycle of any virus is to make progeny viruses and virus life cycles contain many common elements. Place the following steps in proper order: Transcription (mRNA synthesis)

a. First
b. Second
c. Third
d. Fourth
e. Fifth

A

c. Third

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2
Q

The purpose of the life cycle of any virus is to make progeny viruses and virus life cycles contain many common elements. Place the following steps in proper order: Translation (protein synthesis)

a. First
b. Second
c. Third
d. Fourth
e. Fifth

A

d. Fourth

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3
Q

The purpose of the life cycle of any virus is to make progeny viruses and virus life cycles contain many common elements. Place the following steps in proper order: Release of the viral genome from the capsid and entry of the genome into the cell

a. First
b. Second
c. Third
d. Fourth
e. Fifth

A

b. Second

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4
Q

The purpose of the life cycle of any virus is to make progeny viruses and virus life cycles contain many common elements. Place the following steps in proper order: Genome replication

a. First
b. Second
c. Third
d. Fourth
e. Fifth

A

e. Fifth

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5
Q

The purpose of the life cycle of any virus is to make progeny viruses and virus life cycles contain many common elements. Place the following steps in proper order: Attachment of virus to cellular receptor

a. First
b. Second
c. Third
d. Fourth
e. Fifth

A

a. First

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6
Q

Which of the following characteristics is NOT used for classification of viruses?

a. The type of cell in which the virus replicates
b. The presence or absence of a lipid envelope
c. The symmetry of the protein shell
d. The nature of the nucleic acid (DNA or RNA) in the virion

A

a. The type of cell in which the virus replicates

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7
Q

Which of the following nucleic acids can be a viral genome?

a. single-stranded RNA
b. double-stranded RNA
c. single-stranded DNA
d. these can all be viral genomes e. double-stranded DNA

A

d. these can all be viral genomes

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8
Q

Depending on the type of virus, which of the following is a function of the virus capsid?

a. to attach to the correct type of host cell
b. to protect the viral genome from nucleases
c. to ensure delivery of the genome into the host cell
d. to protect the viral genome from damage by UV light
e. all of the above functions are correct

A

e. all of the above functions are correct

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9
Q

The nucleocapsid describes the structure that includes the:

a. capsid and the genome
b. capsid and the envelope
c. envelope and the glycoproteins
d. helical capsid and an envelope
e. icosahedral capsid and an envelope

A

a. capsid and the genome

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10
Q

Where do enveloped viruses get their lipid envelope?

a. it is encoded by the viral genome
b. by budding through a cellular membrane
c. from the nuclear envelope
d. free cellular lipids associate with the capsid proteins after synthesis

A

b. by budding through a cellular membrane

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11
Q

Which of the following is NOT an axis of icosahedral symmetry?

a. threefold
b. twofold
c. fourfold
d. fivefold

A

c. fourfold

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12
Q

Which of the following is true of the 8-stranded antiparallel beta-barrel (jelly roll) structure of many viral capsid proteins?

a. prevents these proteins from interacting with one another
b. ensures tight packing of structural subunits
c. hold neighboring subunits further apart
d. none of the above

A

b. ensures tight packing of structural subunits

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13
Q

The triangulation number, T, of an isosahedral virion refers to

a. the number of structural units (facets) per triangular face
b. the number of crystal structures it can form
c. the number of subunits in the capsid
d. the size of each structural unit (facet) on a triangular face

A

d. the size of each structural unit (facet) on a triangular face

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14
Q

Any viral genome must either already resemble or be copied to which other type of nucleic acid before proteins can be produced?

a. DNA
b. transfer RNA (tRNA)
c. messenger RNA (mRNA)
d. ribosomal RNA (rRNA)

A

c. messenger RNA (mRNA)

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15
Q

Which type of viral genome can be translated as soon as it enters the host cell?

a. dsRNA
b. dsDNA
c. positive (+) strand ssRNA
d. negative (-) strand ssRNA

A

c. positive (+) strand ssRNA

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16
Q

Which of the following processes MUST use the host cell machinery?

a. Translation (protein synthesis)
b. Genome replication
c. Assembly of new virus particles
d. Transcription (mRNA synthesis)

A

a. Translation (protein synthesis)

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17
Q

Which of the following cellular membranes can be chosen for virus budding?

a. The cell plasma membrane
b. All of these may be used
c. The endoplasmic reticulum (ER)
d. The nuclear membrane

A

b. All of these may be used

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18
Q

Most viruses that use a spherical shaped capsid arrange their capsid proteins with which of the following symmetries?

a. cubic
b. tetrahedral
c. icosahedral
d. helical

A

c. icosahedral

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19
Q

During a single growth cycle experiment, the amount (titer) of extracellular and intracellular virus drops in the first hour after infection. What explains this observation?

a. The virus is inactivated by antibodies in the medium
b. The virus is inactivated by cellular enzymes
c. The virus enters the cell and is uncoated
d. The virus binds to the cells in the dish and can’t be released

A

c. The virus enters the cell and is uncoated

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20
Q

Which of the following is an enzyme that most RNA viruses encode in their genome?

a. DNA-dependent RNA polymerase
b. RNA-dependent RNA polymerase
c. DNA-dependent DNA polymerase
d. DNA-dependent RNA polymerase

A

b. RNA-dependent RNA polymerase

21
Q

How are RNA viruses able to mutate so rapidly?

a. Recombination between homologous RNA molecules
b. Their genomes can undergo genetic reassortment
c. RNA-dependent RNA polymerases don’t have a proof-reading activity
d. All of the above

A

d. All of the above

22
Q

All viruses that use a negative-sense RNA genome must package which of the following proteins in their virion?

a. RNA-dependent-RNA-polymerase
b. RNA helicase
c. RNA methylase
d. scaffolding protein

A

a. RNA-dependent-RNA-polymerase

23
Q

Western blot analysis does NOT require which of the following?

a. Detection by immunostaining
b. Transfer to a thin, synthetic membrane
c. Labeling of proteins
d. Fractionation of proteins on a polyacrylamide gel

A

c. Labeling of proteins

24
Q

Which method is NOT used for detecting nucleic acids?

a. polymerase chain reaction (PCR)
b. Southern blotting
c. Electron microscopy
d. Northern blotting

A

c. Electron microscopy

25
Q

What method is most commonly used to propagate viruses in the laboratory?

a. Embryonated eggs
b. Cell culture
c. Laboratory animals
d. Primary animal tissues

A

b. Cell culture

26
Q

Which of the following methods is NOT appropriate for measuring the infectivity of a virus particle?

a. Plaque assay
b. Electron microscopy
c. Transformation assay
d. Endpoint dilution assay

A

b. Electron microscopy

27
Q

Which of the following is a description of a plaque?

a. A viral particle as seen by electron microscopy
b. A region of dead cells in a monolayer of infected cells
c. A skin lesion caused by a virus infection in an animal
d. A button of red blood cells seen in a hemagglutination assay
e. A region of crystallized virus particles in an infected cell

A

b. A region of dead cells in a monolayer of infected cells

28
Q

If the genome of a positive-strand RNA virus, which has been purified away from all of the virion proteins, were to be injected into the cytoplasm of an appropriate host cell, what would happen FIRST?

a. The genome would be copied into complementary negative RNA
b. The genome would be translated by cellular ribosomes
c. The genome would be transcribed by a cellular RNA-dependent-RNA-polymerase
d. The genome would be transcribed by a viral RNA-dependent-RNA-polymerase e. None of the above

A

b. The genome would be translated by cellular ribosomes

29
Q

If the genome of a negative-strand RNA virus, which has been purified away from all of the virion proteins, was injected into the cytoplasm of an appropriate host cell, what would happen first?

a. The genome would be copied into complementary negative RNA
b. The genome would be translated by cellular ribosomes
c. The genome would be transcribed by a cellular RNA-dependent-RNA-polymerase
d. The genome would be transcribed by a viral RNA-dependent-RNA-polymerase
e. None of the above

A

ae. None of the above

30
Q

A packaging sequence is involved in which of the following assembly processes?

a. The assembly of the capsid around the genomic nucleic acid
b. The correct binding of capsid proteins to each other
c. The insertion of the viral glycoproteins in the envelope
d. The acquisition of the envelope by the capsid

A

a. The assembly of the capsid around the genomic nucleic acid

31
Q

Non-enveloped viruses must get their genome past the hydrophobic cell membrane. Some accomplish this by doing which of the following?

a. They cause the plasma membrane to lyse
b. They create a pore through the membrane and extrude the genome directly into the cytoplasm
c. They insert viral proteins into a vesicle membrane
d. They inject their genome into the nucleus via the nuclear pore complex

A

b. They create a pore through the membrane and extrude the genome directly into the cytoplasm

32
Q

Which of the following is NOT a step in viral entry via receptor-mediated endocytosis?

a. The coated vesicles interact with the nuclear pore complex
b. Formation of coated vesicles
c. Binding of the virus to a specific cell surface receptor
d. Diffusion of the virus-receptor complex into clathrin-coated pits

A

a. The coated vesicles interact with the nuclear pore complex

33
Q

Most viruses must exit the endosome before it fuses with a lysosome. Why?

a. Their envelope will not fuse easily with the lysosomal membrane
b. To avoid the very low pH in the lysosome, which causes destructive conformational changes
c. To avoid being degraded by lysosomal proteases and nucleases
d. To enhance their movement towards the nucleus of the cell
e. The pH of the lysosome is too high to induce membrane fusion

A

c. To avoid being degraded by lysosomal proteases and nucleases

34
Q

Before ANY viral genome can be transcribed or replicated in a new host cell it must….

a. be trimmed by cellular nucleases
b. be uncoated in the appropriate compartment of the correct cell type
c. be transported through the receptor mediated endocytosis pathway
d. enter the host cell nucleus and be bound by cellular histone proteins

A

b. be uncoated in the appropriate compartment of the correct cell type

35
Q

How does an RNA-dependent RNA polymerase know where to start copying anRNA template?

a. Recognition of internal sequences or structures
b. Protein-protein interactions can direct the polymerase to the template
c. Recognition of sequences or structures near the 5’ and 3’ ends
d. All of these

A

d. All of these

36
Q

Some viruses have depressions, called “canyons”, on the surface of the virions. Which of the following describes the role that these depressions play?

a. They release the viral genome into the host cell
b. They bind to the host cell receptor
c. They maintain the stability of the capsid
d. They adhere to the envelope

A

b. They bind to the host cell receptor

37
Q

For retroviruses, reverse transcriptase produces a final product of:

a. ssRNA
b. dsDNA
c. ssDNA
d. dsRNA

A

b. dsDNA

38
Q

What do RNA helicases do?

a. Unwind the genomes of double-stranded RNA viruses
b. Unwind secondary structures in template RNAs
c. Prevent extensive base-pairing between template RNA and the nascent complementary strand
d. All of the above

A

d. All of the above

39
Q

During viral infections, cellular defense mechanisms such as RNA interference and the interferon response are triggered by what kind of nucleic acid?

a. negative (-) strand ssRNA
b. dsRNA
c. positive (+) strand ssRNA
d. dsDNA

A

b. dsRNA

40
Q

refer to mRNA synthesis mechanisms used by various viruses we discussed in class. Coronaviruses like MERS and SARS synthesize up to 14 proteins. Given that eukaryotic mRNAs are monocystronic, how do these viruses accomplish this?

a. They use a segmented genome
b. They synthesize a nested set of mRNAs with identical 5’ and 3’ ends
c. The genome serves as the mRNA and a single polyprotein translated from it is cleaved into individual proteins
d. They synthesize five mRNAs by a stop-start mechanism of translation

A

b. They synthesize a nested set of mRNAs with identical 5’ and 3’ ends

41
Q

refer to mRNA synthesis mechanisms used by various viruses we discussed in class. Viruses like VSV synthesize several proteins including a viral RdRp and a nucleocapsid protein. Given that eukaryotic mRNAs are monocystronic, how do these viruses accomplish this?

a. They use a segmented genome
b. They synthesize a nested set of mRNAs with identical 5’ and 3’ ends
c. The genome serves as the mRNA and a single polyprotein translated from it is cleaved into individual proteins
d. They synthesize unique individual mRNAs by a stop-start mechanism of transcription

A

d. They synthesize unique individual mRNAs by a stop-start mechanism of transcription

42
Q

refer to mRNA synthesis mechanisms used by various viruses we discussed in class. Viruses like poliovirus and Zika virus synthesize both structural and nonstructural proteins via a common mechanism. Given that eukaryotic mRNAs are monocystronic, how do these viruses accomplish this?

a. They use a segmented genome
b. They synthesize a nested set of mRNAs with identical 5’ and 3’ ends
c. The genome serves as the mRNA and a single polyprotein translated from it is cleaved into individual proteins
d. They synthesize five mRNAs by a stop-start mechanism of translation

A

c. The genome serves as the mRNA and a single polyprotein translated from it is cleaved into individual proteins

43
Q

refer to mRNA synthesis mechanisms used by various viruses we discussed in class. Viruses like influenza have solved this problem in a different way. Given that eukaryotic mRNAs are monocystronic, how does this virus accomplish this?

a. It uses a segmented genome
b. It synthesizes a nested set of mRNAs with identical 5’ and 3’ ends
c. The genome serves as the mRNA and a single polyprotein translated from it is cleaved into individual proteins
d. It synthesizes five mRNAs by a stop-start mechanism of translation

A

a. It uses a segmented genome

44
Q

refer to the following unknown virus. You received a sample of an unknown virus and you’re trying to identify it. Please use this table to answer the following questions. You should answer them in the order they’re given so that you can rule out the wrong answers and identify the unknown by a process of elimination. You obtained electron micrographs of your virus that look like the micrograph shown here. Your micrographs show that the virus has a lipid envelope. This allows you to rule out which of the following?

a. Rabies virus
b. Bunyamwera virus
c. Poliovirus
d. MERS coronavirus
e. Influenza A virus

A

c. Poliovirus

45
Q

refer to the following unknown virus. You received a sample of an unknown virus and you’re trying to identify it. Please use this table to answer the following questions. You should answer them in the order they’re given so that you can rule out the wrong answers and identify the unknown by a process of elimination.

You isolate the nucleic acid from your virus particles and determine that it is RNA. You determine that it is single-stranded and of negative (-) polarity. Which one of the following viruses can you rule out now?

a. Rabies virus
b. Bunyamwera virus
c. Poliovirus
d. MERS coronavirus
e. Influenza A virus

A

d. MERS coronavirus

46
Q

refer to the following unknown virus. You received a sample of an unknown virus and you’re trying to identify it. Please use this table to answer the following questions. You should answer them in the order they’re given so that you can rule out the wrong answers and identify the unknown by a process of elimination.

You further analyze your viral RNA by running it on a denaturing agarose gel. Under these conditions, the migration of the nucleic acid is directly proportional to its size: larger molecules migrate slowly while smaller ones migrate more rapidly. You detect the presence of multiple segments of genomic RNA. Which of the following viruses can you rule out now?

a. Rabies virus
b. Bunyamwera virus
c. Poliovirus
d. MERS coronavirus
e. Influenza A virus

A

a. Rabies virus

47
Q

refer to the following unknown virus. You received a sample of an unknown virus and you’re trying to identify it. Please use this table to answer the following questions. You should answer them in the order they’re given so that you can rule out the wrong answers and identify the unknown by a process of elimination.

When you analyze the pattern of mRNA synthesis in cultured cells infected with the virus, you determine that there are eight mRNAs, each of which has a 5’ cap derived from the host. Which additional virus can you rule out now?

a. Rabies virus
b. Bunyamwera virus
c. Poliovirus
d. MERS coronavirus
e. Influenza A virus

A

b. Bunyamwera virus

48
Q

refer to the following unknown virus. You received a sample of an unknown virus and you’re trying to identify it. Please use this table to answer the following questions. You should answer them in the order they’re given so that you can rule out the wrong answers and identify the unknown by a process of elimination.

The answers to the previous four questions allow you to identify your unknown virus as which of the following viruses?

a. Rabies virus
b. Bunyamwera virus
c. Poliovirus
d. MERS coronavirus
e. Influenza A virus

A

e. Influenza A virus

49
Q

refer to the following unknown virus. You received a sample of an unknown virus and you’re trying to identify it. Please use this table to answer the following questions. You should answer them in the order they’re given so that you can rule out the wrong answers and identify the unknown by a process of elimination.

A

respond to stimuli (alive) independent metabolism and protein synthesis (not)

Virology (3 decks)

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