Question 1

A researcher is studying a single plant infected with tobacco mosaic virus (TMV). She crushes three of the plant's leaves in a small amount of water and stores the sample in the refrigerator overnight. The next day she sprays the mixture onto a new set of tobacco plants she had recently trimmed and repotted. Which of the following results will most likely occur?

Accepted Answer

Tobacco mosaic virus (TMV) is a highly infectious virus that can easily be transmitted from one plant to another through mechanical means, such as the application of infected plant material. When the researcher sprays the mixture containing TMV onto new plants, it is likely that these plants will develop the typical symptoms of TMV infection and, in turn, be capable of transmitting the disease to other plants.

Question 2

The difference between vertical and horizontal transmission of plant viruses is that vertical transmission ________.

Accepted Answer

Vertical transmission involves the transfer of viruses from a parent plant to its offspring, typically through seeds, while horizontal transmission refers to the spread of viruses from one plant to another, which does not involve parent-offspring transfer.

Question 3

Which of the following statements correctly describes vaccines and how they help prevent viral infection?

Accepted Answer

Vaccines often contain inactivated (killed) viruses or parts of the virus structure (like proteins) that are not capable of causing disease. These components stimulate the immune system to respond, preparing it to fight the actual virus if the person is exposed to it in the future. Vaccines do not contain active or functional pathogens that can cause disease in the person receiving the vaccine.

Question 4

Which of the following correctly describes a strategy that bacteria have evolved to defend against infection by phage?

Accepted Answer

The CRISPR-Cas system is a bacterial immune mechanism that allows bacteria to "remember" and destroy DNA from specific phages that have previously infected them, providing a form of acquired immunity against those phages.

Question 5

Which of the following types of viral genomes could be copied using reverse transcriptase?

Accepted Answer

Reverse transcriptase is an enzyme that synthesizes DNA from an RNA template, which means it is used by viruses with ssRNA (single-stranded RNA) genomes to convert their RNA into DNA.

Question 6

A population of viruses with similar characteristics is called a ________.

Accepted Answer

The answer of A population of viruses with similar characteristics...

Question 7

Which of the following viruses would most likely contain reverse transcriptase?

Accepted Answer

Reverse transcriptase is an enzyme used by RNA-based lysogenic viruses, such as retroviruses, to convert their RNA genome into DNA, which can then integrate into the host's genome.

Question 8

Humans have harmless E. coli strains that reside in the intestines. O157:H7 is an E. coli strain reported to cause several food poisoning deaths. Evidence suggests that the virulence of O157:H7 is caused by genes from a virus that infects bacteria. Considering this evidence, which of the following statements most likely explains how the O157:H7 population acquired the genetic variation that distinguishes it from the harmless E. coli strains?

Accepted Answer

The process described in D, where a virus infects a bacterium and integrates its genome into the bacterial DNA, allowing every new bacterium to replicate with a copy of the viral genome, is known as lysogeny. This is a plausible explanation for how E. coli O157:H7 acquired virulence factors from a virus.

Question 9

Which of the following responses explain why the apparent high rate of mutation in RNA viruses?

Accepted Answer

RNA virus genome replication lacks the proofreading mechanisms that are present in DNA replication, leading to a higher rate of mutation.

Question 10

Which of the following best defines prions?

Accepted Answer

Prions are misfolded proteins that can cause disease by inducing normal versions of the protein to also misfold. They are known for their role in diseases such as Creutzfeldt-Jakob disease in humans and bovine spongiform encephalopathy (mad cow disease) in cattle.

Question 11

Which of the following human diseases is caused by a virus that requires reverse transcriptase to transcribe its genome inside the host cell?

Accepted Answer

AIDS is caused by the Human Immunodeficiency Virus (HIV), which is a retrovirus. Retroviruses use reverse transcriptase to transcribe their RNA genome into DNA inside a host cell.

Question 12

Viruses require host cell's machinery to make copies of themselves. However, some viruses that infect humans require mechanisms that do not normally occur in human cells. Which of the following describes how the viruses can replicate in human cells?

Accepted Answer

Viruses often carry genes that encode for specialized enzymes necessary for their replication, which are not naturally present in the host cells. These enzymes enable the virus to replicate by using the host's cellular machinery in ways that the host cell itself does not normally operate.

Question 13

If a viral host cell has a mutation that interferes with the addition of carbohydrates to proteins during processing in the Golgi apparatus, which of the following processes is most likely to occur?

Accepted Answer

The addition of carbohydrates to proteins (glycosylation) in the Golgi apparatus is crucial for the proper folding, stability, and function of many proteins, including those on the surfaces of viruses. If this process is disrupted, the resulting viruses may have improperly formed surface proteins, which could impair their ability to bind to and infect host cells.

Question 14

A virus consisting of a single strand of RNA, which is reverse transcribed into complementary DNA, is referred to as a ________.

Accepted Answer

Retroviruses are characterized by their ability to reverse transcribe their RNA genome into DNA, which is then integrated into the host cell's genome. This process is facilitated by the enzyme reverse transcriptase, which the virus carries.

Question 15

If a viral host cell has a mutation that interferes with the addition of carbohydrates to proteins during processing in the Golgi apparatus, which of the following processes is most likely to occur?

Accepted Answer

Glycosylation, the addition of carbohydrates to proteins, often occurs in the Golgi apparatus. Viral envelope proteins, which are glycoproteins, require this modification for proper function and localization, including incorporation into the host plasma membrane. Without glycosylation, these proteins may not be correctly processed or localized, impacting the virus's ability to assemble and exit the cell. Capsid and core proteins are not typically glycosylated, and the mutation described would not directly prevent viral reproduction within the host cell, only potentially affect the virus's ability to infect other cells.

Question 16

Azidothymidine (AZT) is a reverse transcriptase inhibitor that was part of the first class of antiviral drugs developed to treat HIV infection. Which of the following correctly describes how these drugs inhibited HIV infection?

Accepted Answer

Azidothymidine (AZT) and other reverse transcriptase inhibitors work by binding to the viral reverse transcriptase enzyme, thereby preventing it from synthesizing DNA from the viral RNA template. This stops the virus from replicating its genome within the host cell.

Question 17

A few minutes of incubation at room temperature in the laboratory will inactivate HIV, but the flu virus is still active after incubating for several hours. What are the practical consequences of these findings?

Accepted Answer

The flu virus's ability to remain active for several hours at room temperature compared to HIV's rapid inactivation suggests that the flu virus can be transmitted more easily from person to person, as it can survive longer on surfaces and in the air.

Question 18

Which of the following processes can be effective in preventing the onset of viral infection in humans?

Accepted Answer

Vaccination is an effective method to prevent viral infections by stimulating the immune system to recognize and fight specific viruses before exposure.

Question 19

Which of the following statements correctly describes a characteristic of viral infections in plants?

Accepted Answer

Viral infections in plants can indeed spread within a plant through plasmodesmata, which are microscopic channels that traverse the cell walls of plant cells, facilitating the transport of molecules and communication between cells. This characteristic allows viruses to move from an infected cell to adjacent healthy cells, thereby spreading the infection throughout the plant.

Question 20

Which of the following statements correctly describes a difference between viruses and prions?

Accepted Answer

Viruses require the host's DNA replication machinery to replicate their genomes, whether RNA or DNA. Prions, on the other hand, are infectious proteins that replicate by inducing misfolding of normal cellular proteins, particularly in the brain, using the host's protein synthesis and folding machinery, not nucleic acid replication machinery.

Quiz 26: Introduction to Viruses

The difference between vertical and horizontal transmission of plant viruses is that vertical transmission ________.

Which of the following statements correctly describes vaccines and how they help prevent viral infection?

Which of the following correctly describes a strategy that bacteria have evolved to defend against infection by phage?

Which of the following types of viral genomes could be copied using reverse transcriptase?

A population of viruses with similar characteristics is called a ________.

Which of the following viruses would most likely contain reverse transcriptase?

Which of the following responses explain why the apparent high rate of mutation in RNA viruses?

Which of the following best defines prions?

Which of the following human diseases is caused by a virus that requires reverse transcriptase to transcribe its genome inside the host cell?

Viruses require host cell's machinery to make copies of themselves. However, some viruses that infect humans require mechanisms that do not normally occur in human cells. Which of the following describes how the viruses can replicate in human cells?

If a viral host cell has a mutation that interferes with the addition of carbohydrates to proteins during processing in the Golgi apparatus, which of the following processes is most likely to occur?

A virus consisting of a single strand of RNA, which is reverse transcribed into complementary DNA, is referred to as a ________.

If a viral host cell has a mutation that interferes with the addition of carbohydrates to proteins during processing in the Golgi apparatus, which of the following processes is most likely to occur?

Azidothymidine (AZT) is a reverse transcriptase inhibitor that was part of the first class of antiviral drugs developed to treat HIV infection. Which of the following correctly describes how these drugs inhibited HIV infection?

A few minutes of incubation at room temperature in the laboratory will inactivate HIV, but the flu virus is still active after incubating for several hours. What are the practical consequences of these findings?

Which of the following processes can be effective in preventing the onset of viral infection in humans?

Which of the following statements correctly describes a characteristic of viral infections in plants?

Which of the following statements correctly describes a difference between viruses and prions?