Deck 5: Single-Stranded Rna Bacteriophages

Question 1

The viral polymerase complex from the RNA phage Q $\beta$ contains which of the following host cell proteins?

A)Host Factor
B)S1 ribosomal protein
C)EF-Tu translational factor
D)EF-Ts translational factor
E)All of the above are part of the complex.

Answer 1

All of the above are part of the complex.

Question 2

The discovery of the ssRNA phages was useful to scientists working on which of the following processes:

A)Structure of ribosomal RNA
B)Translation of messenger RNA
C)Structure of proteins
D)Transcription of messenger RNA
E)Replication of DNA

Answer 2

B

Question 3

Which of the following proteins in the virions of the ssRNA phages binds to the F-pilus during virus attachment and entry?

A)Lysis protein
B)Attachment protein
C)Coat protein
D)Maturation protein
E)Replicase protein

Answer 3

D

Question 4

When an RNA phage virion is assembled with either a defective or missing maturation protein,which of the following occurs?

A)The viral RNA genome is more sensitive to RNAse degradation.
B)The virion is more sensitive to protease degradation.
C)The virion is unstable and disassembles easily in the environment.
D)The virion is not able to carry out genome replication.
E)The tail cannot inject the genome into the host cell.

Question 5

How is the structure of an RNA phage virion different from the structure of the virion of many dsDNA phages?

A)They have much shorter tails than the DNA phages.
B)The heads do not use icosahedral symmetry.
C)The icosahedral head has a very large triangulation number.
D)They are solely composed of a helical nucleocapsid.
E)They lack the tail structure used to inject the genome into the host cell.

Question 6

Why are ssRNA phages used as an index organism to detect the presence of pathogenic enteroviruses in the sewage treatment process?

A)The RNA phage are smaller than the pathogenic viruses.
B)The RNA phage are easier to inactivate than the pathogenic viruses.
C)The RNA phage are more stable than the pathogenic viruses.
D)The RNA phage are easier to quantify using a plaque assay than the pathogenic viruses.
E)The RNA phage are easier to see with an electron microscope than the pathogenic viruses

Question 7

In the ssRNA phage MS2,the replicase protein binds to the start codon of the coat protein gene.Which of the following describes the reason for this binding?

A)It prevents replication and translation from occurring simultaneously.
B)It initiates synthesis of the minus-strand copy of the genome.
C)It enhances binding of the ribosome to the coat protein gene.
D)It disrupts the stem-loop structure that prevents replication of the viral genome.
E)It exposes the 3' end of the genome which allows the replicase to begin RNA synthesis.

Question 8

Site directed mutagenesis of the MS2 genome was carried out to abolish the MJ stem structure that is just upstream of the start codon of the replicase gene.Which of the following describes the result of this experiment?

A)The coat protein was unable to bind to the viral genome.
B)The maturation protein was unable to bind to the stem-loop.
C)The ribosome could no longer bind to the start codon for the replicase gene.
D)The replicase protein was unable to bind to the viral genome.
E)Translation of replicase gene increased in the absence of coat protein translation.

Question 9

What is the function of Host Factor during the replication of the Q $\beta$ RNA genome?

A)It delays the folding of the RNA into its final secondary structure.
B)It makes the 3' end of the genome more accessible to the replicase enzyme.
C)It adds a non-template A nucleotide to the 5' end of the minus strand.
D)It facilitates binding of the replicase protein to the coat protein start codon.
E)It prevents binding of the replicase enzyme to the 5' end of the genome.

Question 10

Translational readthrough occasionally occurs in the coat protein gene of the ssRNA phage Q $\beta$ .Which of the following describes this process?

A)The stop codon (UGA)is read as a tryptophan codon (UGG).
B)The RNA-dependent RNA polymerase reads into the next gene.
C)The RNA-dependent RNA polymerase inserts an extra base in this gene.
D)The ribosome shifts back one base and reads a different reading frame.
E)The ribosome shifts forward one base and reads a different reading frame.

Question 11

The replicase enzyme of the ssRNA phage Q $\beta$ has been used by scientists to do which of the following?

A)Synthesize RNA molecules from a DNA template.
B)Measure small amounts of target RNA molecules in a sample.
C)Measure the levels of pathogenic viruses in drinking water.
D)Amplify DNA molecules in a sample.
E)Fuse two pieces of RNA together.

Question 12

Which of the following structures found on E.coli cells is required for infection with a ssRNA phage?

A)Cell wall
B)Lipopolysaccharide
C)F-pili
D)Cell surface receptor
E)All of the above are required.

Question 13

In the ssRNA phage MS2,the maturation protein is only produced after which of the following events occurs?

A)The synthesis of the negative strand of the viral genome.
B)The synthesis of the positive strand of the viral genome.
C)Packaging of the viral genome into new capsids.
D)Translation of the coat protein.
E)Folding of the newly synthesized genome into the stable secondary structure.

Question 14

In the ssRNA phage MS2,binding of the coat protein to which of the following RNA structures acts to initiate packaging of the viral RNA into the capsids.

A)The 5' end of the genome
B)The 3' end of the genome
C)The MJ stem loop
D)The start codon of the coat protein gene
E)The operator stem loop

Question 15

Which of the following genes from the ssRNA phage MS2 is translated immediately upon entry of the viral genome into the host cell?

A)Maturation protein gene
B)Lysis protein gene
C)Coat protein gene
D)Replicase gene
E)A1 gene

Question 16

In the ssRNA phage MS2,translation of the lysis protein gene is dependent on which of the following events?

A)Replication of the viral genomic RNA.
B)Initiation of translation of the replicase gene.
C)Binding of the coat protein to the nucleation site on the genome.
D)Termination of translation of the coat protein gene.
E)Initiation of translation of the maturation gene.

Question 17

In the ssRNA phage MS2,the replicase and lysis proteins are NOT produced immediately upon entry of the viral genome.Which of the following mechanisms is the primary explanation for why this happens?

A)The start codons for these genes are buried in a very stable stem-loop structure.
B)They have Shine-Dalgarno sequences that do not bind well to the ribosome.
C)They both contain non-canonical TTG start codons.
D)The genes encoding these proteins are uncoated from the capsid until later.
E)The initiator tRNA does not bind well to the start codons of these genes.

Question 18

Once the RNA genome of Q $\beta$ is released into the host cell,which of the following describes the first step in the viral replication cycle?

A)Translation of the genome by viral ribosomes to produce proteins.
B)Translation of the genome by cellular ribosomes to produce proteins.
C)Replication of the genome by a viral enzyme.
D)Replication of the genome by a cellular enzyme.
E)Cleavage of the genome into two fragments.

Question 19

The bacteriophage MS2,which has a ssRNA genome,must produce many more copies of the coat protein than of the replicase and lysis proteins.Which of the following genome features controls how much of each protein is produced?

A)Translational control sequences at the 3' end of the genome
B)Translational control sequences at the 5' end of the genome
C)Secondary structure of the RNA genome
D)The strength of the transcriptional promoters
E)The location of the transcriptional terminators

Question 20

In the ssRNA phage Q $\beta$ the synthesis of the plus strand RNA genome from the negative strand template does not require the ribosomal S1 protein.Which of the following explains why?

A)The minus strand is shorter and takes less time to replicate
B)The minus strand lacks the secondary structure that prevents replication.
C)There is no competition between binding of the replicase enzyme and the ribosome.
D)The replicase enzyme is more processive when copying the minus strand.
E)The minus strand has a lower GC content than the plus strand.

Question 21

Replication of the RNA genome by the replicase enzyme from the phage Q $\beta$ is completely independent of host cell proteins.

Question 22

Replication and translation can occur simultaneously on a single molecule of genomic RNA from the ssRNA phage MS2.

Question 23

Why must the ssRNA phage,like MS2 and Qb,prevent the viral genome from simultaneously being translated by a ribosome and replicated by the replicase enzyme? Describe the mechanism that these viruses use to prevent this from happening.

Question 24

During the replication cycle of the ssRNA phage MS2,the lysis gene can not be translated in the absence of translation of the coat protein gene.

Question 25

The translation of the maturation protein from a newly synthesized positive strand genome in the phage MS2 depends on delayed folding of the RNA into its final secondary structure.

Question 26

The RNA phages do not use a tail assembly to inject their genome through the cell wall of the host cell.How do they get their genome into the host cell?