Question 1

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

Accepted Answer

A

Question 2

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

Accepted Answer

Translation of the lysis protein gene in MS2 is dependent on the termination of translation of the coat protein gene, as the ribosome must pass through the coat protein gene to access the lysis gene.

Question 3

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?

Accepted Answer

This binding prevents replication and translation from occurring simultaneously, ensuring that the processes do not interfere with each other.

Question 4

The viral polymerase complex from the RNA phage Qb contains which of the following host cell proteins?

Accepted Answer

The viral polymerase complex from the RNA phage Qβ includes host cell proteins such as Host Factor, S1 ribosomal protein, and EF-Tu and EF-Ts translational factors, making all the listed options correct components of the complex.

Question 5

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.

Accepted Answer

The answer of In the ssRNA phage MS2, binding of...

Question 6

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

Accepted Answer

The discovery of ssRNA phages was particularly useful to scientists working on the translation of messenger RNA (mRNA) because these phages contain RNA that serves directly as mRNA, which can be directly translated into proteins by the host cell's machinery. This provided a simple and effective model system for studying the process of translation.

Question 7

What is the function of Host Factor during the replication of the Qb RNA genome?

Accepted Answer

Host Factor helps in unwinding and denaturing the 3' end of the Qb RNA genome, making it more accessible to the replicase enzyme, which facilitates replication.

Question 8

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?

Accepted Answer

The secondary structure of the RNA genome plays a crucial role in controlling the translation of different proteins in bacteriophages like MS2. This structure can influence the accessibility of ribosome binding sites, thereby affecting how much of each protein is produced.

Question 9

The replicase enzyme of the ssRNA phage Qb has been used by scientists to do which of the following?

Accepted Answer

The replicase enzyme of the ssRNA phage Qb is used in techniques like the Q-beta replicase assay to amplify and measure small amounts of target RNA molecules in a sample.

Question 10

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

Accepted Answer

The answer of In the ssRNA phage MS2, the maturation...

Question 11

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

Accepted Answer

The maturation protein in ssRNA phages is responsible for binding to the F-pilus of the host bacterium during the initial stages of virus attachment and entry.

Question 12

Translational readthrough occasionally occurs in the coat protein gene of the ssRNA phage Qb.Which of the following describes this process?

Accepted Answer

Translational readthrough involves the ribosome misinterpreting a stop codon as a sense codon, allowing translation to continue beyond the normal termination point. In this case, the stop codon UGA is read as the tryptophan codon UGG.

Question 13

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

Accepted Answer

The first step in the viral replication cycle of Qb, an RNA virus, involves the translation of its RNA genome by the host cell's ribosomes to produce viral proteins. Viruses lack the cellular machinery for protein synthesis and rely on the host cell's ribosomes for this process.

Question 14

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?

Accepted Answer

The start codons for these genes are buried in a very stable stem-loop structure, which prevents ribosomal binding and translation initiation. As a result, the production of these proteins is delayed until later in the viral life cycle.

Question 15

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?

Accepted Answer

The answer of Site directed mutagenesis of the MS2 genome...

Question 16

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

Accepted Answer

RNA phages lack the tail structure used to inject the genome into the host cell, whereas dsDNA phages have a tail that serves this purpose.

Question 17

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

Accepted Answer

The coat protein gene is translated immediately upon entry of the viral genome into the host cell, as it is required for the assembly of new virions. The maturation protein gene is involved in the processing of the viral RNA during replication, while the lysis protein gene is involved in the release of mature virions from the host cell. The replicase gene is responsible for replication of the viral genome, and the A1 gene is involved in inhibition of host cell gene expression.

Question 18

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

Accepted Answer

F-pili are the structures on E. coli cells that are required for infection with certain types of bacteriophages, including some ssRNA phages. These pili serve as attachment points for the phages to bind to the bacterial cell.

Question 19

In the ssRNA phage Qb 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?

Accepted Answer

The synthesis of the plus strand RNA genome from the negative strand template in the ssRNA phage Qβ does not require the ribosomal S1 protein because there is no competition between the binding of the replicase enzyme and the ribosome. This allows the replicase enzyme to efficiently bind and replicate the negative strand without interference from ribosomal components, which is crucial for the synthesis of the plus strand RNA.

Question 20

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

Accepted Answer

ssRNA phages are used as an index organism because they are easier to quantify using a plaque assay than pathogenic enteroviruses. This allows for a more accurate assessment of the efficacy of sewage treatment processes. Additionally, the RNA phages have similar properties to pathogenic enteroviruses in terms of size and structure, making them a good indicator of their presence in sewage.

Quiz 5: Single-Stranded RNA Bacteriophages