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Virology > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

Which of the following is NOT a step in the interferon response to doubel-stranded RNA?

a. Binding of PKR (the dsRNA induced protein kinase) to dsRNA
b. Auto-phosphorylation of PKR to activate its kinase activity
c. Cleavage of the dsRNA into siRNAs by Dicer
d. Phosporylation of eIF2alpha, which is then no longer able to recycle GDP to the initiation complex, and translation stops

A

c. Cleavage of the dsRNA into siRNAs by Dicer

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2
Q

Which of the following strategies are used by viruses to allow translation of multiple proteins from a single RNA genome?

a. Polyprotein synthesis in which a single precursor protein is cleaved into individual viral polypeptides
b. Reinitiation of translation at an AUG downstream of a termination codon
c. Suppression of termination (read-through of a termination codon)
d. Risosomal frameshifting, in which ribosomes can move into another overlapping reading frame and continue translation in the reading frame
e. All of the above strategies are used

A

e. All of the above strategies are used

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3
Q

Some viruses shut-off host cellular translation to ensure that only viral mRNAs are translated efficiently. Which of the following mechanisms is NOT used to shut-off host translation?

a. Cleavage of eIF4G (a component of the initiation complex eIF4F) so that capped mRNAs can’t be translated
b. Removal of the 5’ cap from cellular mRNAs and transfer of this 5’ cap to a viral mRNA
c. Displacement of the polyA binding protein (Pab1p) from the eIF4F initiation complex so that polyadenylated mRNAs in the complex are replaced with viral mRNAs lacking a polyA tail
d. Enzymatic cleavage to remove the polyA tail

A

d. Enzymatic cleavage to remove the polyA tail

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4
Q

Which of the following virus genome DOES NOT contain an IRES element?

a. cricket paralysis virus (CrPV)
b. encephalomyocarditis virus (EMCV)
c. influenza virus
d. hepatitis C virus (HCV)

A

c. influenza virus

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5
Q

How do ribosomes recognize the majority (over 90%) of the cellular and viral mRNAs?

a. Recognition of the 5’ cap and sometimes the polyA tail by a complex of cellular proteins, which then scans to the first AUG initiation codon
b. Binding to internal ribosome entry sites
c. Recognition of only the polyA tail by a complex of cellular proteins, which then scans to the first AUG initiation codon
d. Neither the 5’ cap nor the 3’ polyA tail is involved in recognition of MOST cellular and viral mRNAs

A

a. Recognition of the 5’ cap and sometimes the polyA tail by a complex of cellular proteins, which then scans to the first AUG initiation codon

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6
Q

Amino acids are added to tRNAs by which enzyme?

a. DNA polymerase alpha-primase
b. Aminoacyl-tRNAs synthetase
c. rRNA
d. RNA polymerase II

A

b. Aminoacyl-tRNA synthetase

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7
Q

Which of the following is NOT a component of the translation machinery?

a. Ribosomes
b. Charged tRNAs
c. Translation proteins
d. Transcription factors

A

d. Transcription factors

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8
Q

Which of the following covalent modifications is involved in RNA processing?

a. 5’ capping (addition of m7Gppp to the 5’ end)
b. 3’ polyadenylation
c. splicing
d. RNA editing
e. All of the above

A

e. All of the above

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9
Q

What is the function of the cap structure on the 5’ end of viral and cellular mRNAs?

a. Protect mRNAs from 5’-exonucleases
b. Allow recognition of 5’-terminal exons of pre-mRNAs made by RNA polymerase II
c. Direct efficient translation of most viral and cellular mRNAs
d. All of the above

A

d. All of the above

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10
Q

Which of the following viruses can stimulate entry of slow-growing or resting cells (in Go) back into the cell cycle?

a. Adenoviruses
b. Herpesviruses
c. Polyomavirus
d. All of the above

A

d. All of the above

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11
Q

Which of the following viruses does NOT use the host cellular machinery to replicate its DNA?

a. Adenovirus
b. Vaccinia virus
c. Herpes simplex virus
d. Parvovirus

A

b. Vaccinia virus

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12
Q

How does leading strand synthesis differ from lagging strand synthesis (that is, which of the following statements is true)?

a. Only the leading strand involves synthesis of a primer and Okazaki fragment by the DNA polymerase alpha-primase complex
b. Only the lagging strand involves synthesis of the new (nascent) strand by DNA polymerase delta
c. Leading strand synthesis is continuous, while lagging strand synthesis is discontinuous and requires initiation at multiple sites progressively further from the origin of replication
d. Only lagging strand synthesis requires the Pcna and Rf-C proteins as accessory factors

A

c. Leading strand synthesis is continuous, while lagging strand synthesis is discontinuous and requires initiation at multiple sites progressively further from the origin of replication

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13
Q

Which of the following is NOT part of the SV40 minimal (core) origin of DNA replication?

a. an AT-rich element
b. a binding site for the SV40 large T antigen that consists of a 27-bp perfect palindrome
c. an early imperfect palindrome (EP) that undergoes a conformational change after large T binds to the origin
d. an enhancer

A

d. an enhancer

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14
Q

Which of the following viruses does NOT transcribe its viral genes in a reproducible and precise sequence, using early (and sometimes immediate early) and late promoters?

a. herpes simplex type 1 (HSV-1)
b. None of these (all of these viruses do this)
c. adenovirus
d. SV40

A

b. None of these (all of these viruses do this)

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15
Q

Which of the following is characteristic of a core promoter?

a. They direct assembly of an RNA polymerase-containing complex to begin transcription
b. They contain a TATA sequence 20-35 bp upstream of the initiation site.
c. They can contain initiator sequences that specify accurate but inefficient initiation of transcription in the absence of other promoter sequences.
d. All of these

A

d. All of these

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16
Q

A transcriptional control region contains all EXCEPT which of the following?

a. Distant regulatory sequences like enhancers and silencers
b. Local regulatory sequences
c. A core promoter
d. A primer binding site

A

d. A primer binding site

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17
Q

Which of the following is NOT a regulation pattern established by viral proteins that stimulate RNA polymerase II transcription in mammalian cells?

a. Attenuation
b. A transcriptional cascade
c. A positive autoregulatory loop
d. None of the above; all of these are regulatory circuits are used.

A

a. Attenuation

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18
Q

Which of the following properties are shared by sequence-specific proteins that regulate transcription?

a. They have modular organization
b. They bind to DNA as dimers
c. They are members of families of related proteins that share the same types of DNA-binding and dimerization domains
d. All of the above

A

d. All of the above

19
Q

What does RNaseH do?

a. Degrade free (-) strand RNA
b. Degrade free (+) strand RNA
c. Degrade (+) strand RNA in a DNA-RNA hybrid
d. Degrade (+) strand RNA in an RNA-RNA hybrid

A

c. Degrade (+) strand RNA in a DNA-RNA hybrid

20
Q

Where on the genomic template does reverse transcription start?

a. AT the 5’ end
b. NEAR the 5’ end (100 nucleotides from the 5’ end)
c. AT the 3’ end
d. NEAR the 3’ end (100 nucleotides from the 3’ end)

A

b. NEAR the 5’ end (100 nucleotides from the 5’ end)

21
Q

What does the retrovirus RT enzyme use as a PRIMER to synthesize the (-) strand cDNA copy of the viral genome?

a. Cellular mRNA
b. Cellular tRNA
c. Fragments of the genomic RNA
d. Cellular rRNA

A

b. Cellular tRNA

22
Q

Retroviral reverse transcriptase (RT) has which of the following catalytic activities?

a. RNA-dependent DNA polymerase
b. DNA-dependent DNA polymerase
c. DNA helicase
d. RNaseH
e. All of the above

A

e. All of the above

23
Q

Retrovirus genomes (when found in retrovirus particles) consist of what kind of nucleic acid?

a. Two copies of (+) ssRNA
b. One copy of (+) ssRNA
c. dsDNA
d. Two copies of (-) ssRNA

A

a. Two copies of (+) ssRNA

24
Q

Which of the following steps is NOT involved in integration of the retrovirus cDNA into the host chromosome?

a. Processing of the duplex DNA ends to remove 2 nucleotides
b. Joining of recessed 5’-CA-OH-3’ to target DNA
c. Repair of gaps by cellular enzymes to produce direct repeats of host DNA
d. Sequence-specific binding of integrase protein to retroviral DNA

A

d. Sequence-specific binding of integrase protein to retroviral DNA

25
Q

Members of which of the following virus families have a partially double- stranded DNA genome?

a. Hepadnaviridae
b. Picornaviridae
c. Adenoviridae
d. Polyomaviridae

A

a. Hepadnaviridae

26
Q

A viral genome must be copied to _________ before proteins can be produced.

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

A

a. messenger RNA (mRNA)

27
Q

Cellular defenses such as RNA interference and the interferon response are triggered by what kind of nucleic acid?

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

A

c. dsRNA

28
Q

ALL EXCEPT which of the following covalent modifications is involved in RNA processing?

a. 5’ capping (addition of m7Gppp to the 5’ end)
b. 3’ polyadenylation
c. 5’ polyadenylation
d. splicing

A

c. 5’ polyadenylation

29
Q

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

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

A

b. Electron microscopy

30
Q

Elongation of the growing nucleotide chain (the nascent strand) occurs in which direction?

a. 5’ P of the incoming nucleotide is added to the 3’OH
b. 3’ OH of the incoming nucleotide is added to the 5’ phosphate (P) of the growing DNA or RNA chain
c. 5’ OH of the incoming nucleotide is added to the 3’ P
d. 3’ P of the incoming nucleotide is added to the 5’ OH

A

a. 5’ P of the incoming nucleotide is added to the 3’ OH

31
Q

How does an RNA-dependent RNA polymerase know where to start copy its RNA template?

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

A

d. All of these

32
Q

Which cellular polymerase synthesizes cellular pre-mRNAs and viral mRNAs from DNA templates?

a. RNA polymerase II
b. DNA polymerase
c. RNA polymerase III
d. RNA polymerase I

A

a. RNA polymerase II

33
Q

ALL EXCEPT which of the following activities are characteristic of an RNA helicase?

a. Unwinding of double-stranded RNA virus genomes
b. Unwinding of secondary structures in template RNAs
c. Prevention of extensive base-pairing between template RNA and nascent complementary strand
d. Unwinding of double-stranded DNA virus genomes

A

d. Unwinding of double-stranded DNA virus genomes

34
Q

Which of the following is NOT true of negative strand RNA viruses?

a. Their genomes are arranged into nucleocapsids
b. Their genomes can be used directly as templates for translation
c. Their RdRps must be packaged into progeny particles along with the genomic RNA
d. Their polymerases copy viral RNAs only when they are present in the nucleocapsid

A

b. Their genomes can be use

35
Q

How are RNA viruses able to mutate so rapidly?

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

A

c. All of these

36
Q

Which of the following is NOT part of the SV40 minimal (core) origin of DNA replication?

a. An enhancer
b. An early imperfect palindrome (EP) that undergoes a conformational change after large T binds to the origin
c. An AT-rich element
d. A binding site for the SV40 large T antigen that consists of a 27-bp perfect palindrome

A

a. An enhancer

37
Q

How does SV40 solve the “end problem” in which sequences can be lost from the 3’ end of a dsDNA genome during DNA replication?

a. It uses a 5’-terminal protein
b. It has a circular DNA genome
c. It uses a 3’-terminal protein
d. It encodes a poly(A) tail

A

b. It has a circular DNA genome

38
Q

What is the purpose of the RNA helicases SV40 large T antigen and adenovirus E1A in a viral DNA replication?

a. To advance the replication fork for both leading and lagging strand synthesis
b. To unwind the origin of replication
c. To change the conformation of the primer binding site
d. To recruit single-strand DNA binding proteins

A

d. To recruit single-strand DNA binding proteins

39
Q

What is one major difference between prokaryotic & eukaryotic mRNAs?

a. Prokaryotic mRNAs are polycistronic and eukaryotic ones are monocistronic
b. Prokaryotic mRNAs are monocistronic and eukaryotic ones are polycistronic
c. Both are polycistronic
d. Both are monocistronic

A

a. Prokaryotic mRNAs are polycistronic and eukaryotic ones are monocistronic

40
Q

During translation, initiation involves recruitment of which ribosomal subunit first?

a. The 40S subunit
b. The 60S subunit
c. The entire 80S ribosome
d. None of these

A

a. The 40S subunit

41
Q

How does poliovirus favor its own translation over that of cellular mRNAs?

a. It steals the cap from cellular messages
b. It cleaves the cap-binding protein
c. It cleaves eIF-4G, which results in the cap binding protein being lost
d. It contains a genetically encoded poly(A) tail

A

c. It cleaves eIF-4G, which results in the cap binding protein being lost

42
Q

In a eukaryotic mRNA able to translate cap independently, what sequence element facilitates this ability?

a. A promoter
b. An enhancer
c. An internal ribosome entry site
d. A Shine-Dalgarno sequences

A

c. An internal ribosome entry site

43
Q

What causes translation to terminate?

a. Entry of a methionyl-tRNA into the A site of the ribosome
b. Entry of release factor eRF1 into the P site of the ribosome
c. Entry of release factor eRF1 into the A site of the ribosome
d. Entry of a charged termination tRNA into the ribosome

A

c. Entry of release factor eRF1 into the A site of the ribosome

44
Q

What mechanism has been proposed to explain reinitiation of translation at a downstream initiation codon?

a. A rRNA structure in the 40S ribosomal subunit base pairs with a UGGGA loop upstream of the termination codon, tethering it to the mRA
b. A rRNA structure in the 60S ribosomal subunit basepairs with a UGGGA loop upstream of the termination codon, tethering it to the mRNA
c. The 40S subunit dissociates from the template and backs up one nt
d. The 60S subunit dissociates from the template and backs up one nt

A

a. A rRNA structure in the 40S ribosomal subunit base pairs with a UGGGA loop upstream of the termination codon, tethering it to the mRA

Virology (3 decks)

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