Question 1

Use the figures to answer the question.

Which of the three types of viruses shown would you expect to include glycoproteins?
A) I only
B) II only
C) III only
D) I and II only

Accepted Answer

B

Question 2

The host range of a virus is determined by ________.
A) the enzymes carried by the virus
B) whether its nucleic acid is DNA or RNA
C) the proteins in the host's cytoplasm
D) the proteins on its surface and that of the host

Accepted Answer

The host range of a virus is determined by the specific proteins on its surface and those of the host cell. These proteins must match in order for the virus to enter and infect the host cell. The other options, such as the type of nucleic acid, carried enzymes, or host cytoplasmic proteins, may affect the virus's replication or virulence, but they do not determine its host range.

Question 3

What is the function of reverse transcriptase in retroviruses?
A) It uses viral RNA as a template for DNA synthesis.
B) It converts host cell RNA into viral DNA.
C) It translates viral RNA into proteins.
D) It uses viral RNA as a template for making complementary RNA strands.

Accepted Answer

Reverse transcriptase is an enzyme that converts viral RNA into DNA by using RNA as a template for DNA synthesis. This enables retroviruses to integrate their viral DNA into the host cell genome, allowing the virus to persist in the cell and replicate along with the host cell.

Question 4

Some viruses can be crystallized and their structures analyzed. One such virus is yellow mottle virus, which infects beans. This virus has a single-stranded RNA genome containing about 6,300 nucleotides. Its capsid is 25-30 nm in diameter and contains 180 identical capsomeres. If the yellow mottle virus begins its infection of a cell by using its genome as mRNA, which of the following would you expect to be able to measure when analyzing the reproduction of this virus?
A) replication rate
B) transcription rate
C) translation rate
D) formation of new transcription factors

Accepted Answer

If the virus begins its infection by using its genome as mRNA, we would be able to measure the rate of translation, which is the process of converting the genetic information in mRNA into a protein product. Replication rate refers to the rate at which the virus replicates its genome, which would not be measurable if the virus is using its genome as mRNA. Transcription rate refers to the rate at which DNA is converted to mRNA, but since the virus is already using its genome as mRNA, this measurement would not be applicable. The formation of new transcription factors is not relevant to the reproduction of the virus.

Question 5

Which of the following events or characteristics accounts for someone who has had regular herpesvirus-mediated cold sores or genital sore flare-ups?
A) reinfection by a closely related herpesvirus of a different strain
B) reinfection by the same herpesvirus strain
C) copies of the herpesvirus genome permanently maintained in host nuclei
D) copies of the herpesvirus genome permanently maintained in host cell cytoplasm

Accepted Answer

Once someone is infected with herpesvirus, copies of the virus genome integrate into the host cell's nucleus and are maintained there indefinitely. These copies of the virus can become reactivated, leading to regular cold sore or genital sore flare-ups. Reinfection by a closely related herpesvirus of a different strain (A) is possible but not the primary cause of regular flare-ups. Reinfection by the same herpesvirus strain (B) is not necessary, as copies of the virus are already present in the host cells. Copies of the herpesvirus genome are not maintained in host cell cytoplasm (D).

Question 6

Use the figures to answer the question.

Which of the three types of viruses shown in the figure would you expect to include a capsid(s)?
A) I only
B) II only
C) III only
D) I, II, and III

Accepted Answer

All three types of viruses in the figure have capsids. Type I virus has a helical capsid, type II virus has an icosahedral capsid, and type III virus has both an icosahedral capsid and an outer envelope.

Question 7

The virus genome and viral proteins are assembled into virus particles during which of the following parts of the reproductive cycle?
A) the lytic cycle and the lysogenic cycle in all known host organisms
B) the lysogenic cycle only
C) the lytic cycle only
D) the lytic cycle in all host organisms but the lysogenic cycle only in bacteria

Accepted Answer

During the lytic cycle, the virus genome and viral proteins are assembled into virus particles, which then burst out of the host cell, leading to the death of the host cell. In contrast, during the lysogenic cycle, the virus genome is integrated into the host cell's genome and replicates along with it, without producing virus particles in the short term.

Question 8

Which of the following characteristics is typical of the lytic cycle of a bacteriophage?
A) Viral DNA is incorporated into the host genome.
B) The viral genome replicates without destroying the host.
C) A large number of phages are released at a time.
D) The virus-host relationship usually lasts for generations.

Accepted Answer

The lytic cycle of a bacteriophage typically results in the release of a large number of phages at a time. This occurs when the bacteriophage causes the host cell to lyse, or break open, releasing new viral particles. Choice A is characteristic of the lysogenic cycle, not the lytic cycle. Choice B is not characteristic of either the lytic or lysogenic cycle, as both cycles involve the replication and destruction of the host cell. Choice D is not characteristic of the lytic cycle, as the virus-host relationship is typically short-lived.

Question 9

Which of the following processes can viruses carry out?
A) They can manufacture their own ATP, proteins, and nucleic acids.
B) They can use the host cell to copy themselves and make viral proteins.
C) They can use the host cell to copy themselves and then synthesize their own proteins inside the viral capsid.
D) They can metabolize food and produce their own ATP.

Accepted Answer

Viruses cannot carry out any metabolic processes, so they rely on the host cell to provide the necessary energy and resources for replication. They do not have the machinery to synthesize their own ATP, proteins, or nucleic acids. Instead, they hijack the host cell's machinery to make copies of themselves and assemble new viral particles.

Question 10

In many ways, the regulation of the genes of a particular group of viruses will be similar to the regulation of the host genes. Therefore, which of the following regulation mechanisms would you expect of the genes of a bacteriophage?
A) regulation via acetylation of histones
B) positive control mechanisms rather than negative
C) control of more than one gene in an operon
D) reliance on transcription activators

Accepted Answer

Bacteriophages, which infect bacteria, often use operons to regulate multiple genes simultaneously, similar to their bacterial hosts.

Question 11

Use the figure to answer the question.

In the figure, when new viruses are being assembled at the point marked IV, what mediates the assembly?
A) host cell chaperones
B) assembly proteins coded for by the host nucleus
C) assembly proteins coded for by the viral genes
D) no mediator is required; the new viruses self-assemble

Accepted Answer

The answer of Use the figure to answer the question.

In...

Question 12

Use the following information to answer the question.
Poliovirus is an RNA virus of the picornavirus group, which uses its RNA as mRNA. At its 5′ end, the RNA genome has a viral protein (VPg) instead of a 5′ cap. This is followed by a non-translated leader sequence, and then a single long protein-coding region (~7,000 nucleotides), followed by a poly-A tail. Observations were made that used radioactive amino acids similar in structure to those that are found in viruses and other organisms. Short-period use of the radioactive amino acids result in labeling of only very long proteins, while longer periods of labeling result in several different short polypeptides.
What conclusion is most consistent with the results of the radioactive labeling experiment?
A) Host cell ribosomes only translate the viral code into short polypeptides.
B) The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones.
C) The RNA is translated into short polypeptides, which are subsequently assembled into large ones.
D) The large radioactive polypeptides are coded by the host, whereas the short ones are coded for by the virus.

Accepted Answer

The fact that short periods of labeling only result in labeling of very long proteins, while longer periods of labeling result in several different short polypeptides suggests that the RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones. This is consistent with the information given about the structure of the RNA genome, which has a single long protein-coding region followed by a poly-A tail.

Question 13

Use the following figure and information to answer the question.

Cells were infected with approximately 1,000 copies of either virus A or virus B at the 0 time point. At five-minute intervals, a sample of the virus and cell mixture was removed. The intact cells were removed from the sample, and the number of viruses per milliliter of culture was determined.
Using the data in the figure, how long does it take for virus B to go through one lytic cycle?
A) 15 minutes
B) 30 minutes
C) 45 minutes
D) 60 minutes

Accepted Answer

The answer of Use the following figure and information to...

Question 14

Use the following figure and information to answer the question(s) below.

Cells were infected with approximately 1,000 copies of either virus A or virus B at the 0 time point. At five-minute intervals, a sample of the virus and cell mixture was removed. The intact cells were removed from the sample, and the number of viruses per milliliter of culture was determined.
Using the data in the figure, how long does it take for virus A to go through one lytic cycle?
A) 15 minutes
B) 30 minutes
C) 45 minutes
D) 90 minutes

Accepted Answer

The answer of Use the following figure and information to...

Question 15

Which of the following descriptions correctly identifies the main structural differences between viruses with envelopes and viruses without envelopes?
A) Viruses with envelopes have their genetic material enclosed by a layer made only of protein.
B) Viruses without envelopes have only a phospholipid membrane, while viruses with envelopes have two membranes, the other one being a protein capsid.
C) Viruses with envelopes have a phospholipid membrane outside their capsid, whereas viruses without envelopes do not have a phospholipid membrane.
D) Both types of viruses have a capsid and phospholipid membrane; but in the viruses without envelopes, the genetic material is between these two membranes, while in the viruses with envelopes the genetic material is inside both membranes.

Accepted Answer

Viruses with envelopes have a phospholipid membrane outside their capsid, whereas viruses without envelopes do not have a phospholipid membrane. Option A is incorrect because viruses with envelopes have a phospholipid membrane as well as a layer of protein around their genetic material. Option B is incorrect because viruses without envelopes do not have any membrane, and those with envelopes have only one membrane, which is a phospholipid membrane. Option D is incorrect because viruses without envelopes do not have a phospholipid membrane.

Question 16

Which of the following statements supports the argument that viruses are nonliving?
A) They do not carry out metabolic processes.
B) Their DNA does not encode proteins.
C) They have RNA rather than DNA.
D) They do not evolve.

Accepted Answer

One of the defining characteristics of living things is that they carry out metabolic processes, such as obtaining energy and using it to carry out chemical reactions. Viruses cannot carry out metabolic processes on their own and require a host cell to do so, supporting the argument that they are nonliving. The other options do not necessarily support the argument that viruses are nonliving.

Question 17

Use the figure to answer the question.

In the figure, at the arrow marked II, what enzyme is being utilized?
A) reverse transcriptase
B) viral DNA polymerase
C) host cell DNA polymerase
D) host cell RNA polymerase

Accepted Answer

The answer of Use the figure to answer the question.

In...

Question 18

Use the following information to answer the question.
The herpesviruses are important enveloped DNA viruses that cause disease in vertebrates and in some invertebrates such as oysters. Some of the human forms are herpes simplex virus (HSV) types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these three actively infects nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can later reactivate, replicate again, and infect others.
In electron micrographs of HSV infection, it can be seen that the intact virus initially reacts with cell-surface proteoglycans, then with specific receptors. This is later followed by viral capsids docking with nuclear pores. Afterward, the capsids go from being full to being "empty." Which of the following statements best fits these observations?
A) Viral capsids are needed for the cell to become infected; only the capsids enter the nucleus.
B) The viral envelope is not required for infectivity, since the envelope does not enter the nucleus.
C) Only the genetic material of the virus is involved in the cell's infectivity, and is injected like the genome of a phage.
D) The viral envelope mediates entry into the cell, the capsid mediates entry into the nuclear membrane, and the genome is all that enters the nucleus.

Accepted Answer

The observations suggest that the viral envelope is necessary solely for viral entry into the cell and the capsid is responsible for entry into the nuclear membrane. The genetic material is the only component that enters the nucleus. Therefore, choice D is the best fit for the observations described in the passage.

Question 19

Which of the following characteristics correctly describes retroviruses?
A) They are made up of only a single protein.
B) They can only reproduce by infecting bacteria.
C) They have a single-stranded DNA that acts as a template for DNA synthesis.
D) They have a single-stranded RNA that acts as a template for DNA synthesis.

Accepted Answer

Retroviruses have a single-stranded RNA genome that serves as a template for the reverse transcriptase enzyme to produce a double-stranded DNA molecule that integrates into the host cell genome. Retroviruses cannot infect bacteria as they require host cell machinery to replicate. They are composed of several proteins, not just one.

Question 20

Which of the following statements accurately describes the lysogenic cycle of lambda (λ) phage?
A) After infection, the viral genes immediately turn the host cell into a lambda-producing factory, and the host cell then lyses.
B) Most of the prophage genes are activated by the product of a particular prophage gene.
C) The phage genome is integrated in the host chromosome where it is replicated along with the host genome.
D) The phage DNA is copied and exits the cell as a phage.

Accepted Answer

The lysogenic cycle of lambda phage involves integration of the phage genome into the host chromosome, where it is replicated along with the host genome as a prophage. This allows the viral genes to be passed on to daughter cells during host cell division and can lead to the induction of the lytic cycle under certain conditions. None of the other options accurately describe the lysogenic cycle of lambda phage.

Quiz 19: Viruses

Use the figures to answer the question. Which of the three types of viruses shown would you expect to include glycoproteins?

The host range of a virus is determined by ________.

What is the function of reverse transcriptase in retroviruses?

Which of the following events or characteristics accounts for someone who has had regular herpesvirus-mediated cold sores or genital sore flare-ups?

Use the figures to answer the question. Which of the three types of viruses shown in the figure would you expect to include a capsid(s) ?

The virus genome and viral proteins are assembled into virus particles during which of the following parts of the reproductive cycle?

Which of the following characteristics is typical of the lytic cycle of a bacteriophage?

Which of the following processes can viruses carry out?

In many ways, the regulation of the genes of a particular group of viruses will be similar to the regulation of the host genes. Therefore, which of the following regulation mechanisms would you expect of the genes of a bacteriophage?

Use the figure to answer the question. In the figure, when new viruses are being assembled at the point marked IV, what mediates the assembly?

Which of the following descriptions correctly identifies the main structural differences between viruses with envelopes and viruses without envelopes?

Which of the following statements supports the argument that viruses are nonliving?

Use the figure to answer the question. In the figure, at the arrow marked II, what enzyme is being utilized?

Which of the following characteristics correctly describes retroviruses?

Which of the following statements accurately describes the lysogenic cycle of lambda (λ) phage?