Chapter 17 Review

Which of the three types of viruses shown in the figure above would you expect to include a capsid(s) as part of their overall structure? A) I only B) II only C) III only D) all three

D) all three

Which of the following characteristics determine a virus's host range? 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

D) the proteins on its surface and that of the host

In 1971, David Baltimore described a scheme for classifying viruses based on how the virus produces mRNA, referred to as the Baltimore requirements. The table below shows the results of testing five viruses (A-E) for nuclease sensitivity, the ability of the viral genome to act as an mRNA, and the presence (+) or absence (-) of each virus's own polymerase. Based on the table above, which virus meets the requirements for a bacteriophage? A) A B) B C) C D) D E) E

A) A

You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I.​Treat the substance with nucleases that destroy all nucleic acids and then determine whether it is still infectious. II.​Filter the substance to remove all elements smaller than what can be easily seen under a light microscope. III.​Culture the substance by itself on nutritive medium, away from any plant cells. IV.​Treat the sample with proteases that digest all proteins and then determine whether it is still infectious. If you already knew that the infectious agent was either bacterial or viral, which treatment listed above would allow you to distinguish between these two possibilities? A) I B) II C) III D) IV

A) I

Which of the following statements correctly describes one difference between vertical and horizontal transmission of plant viruses? A) Vertical transmission is transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant. B) Vertical transmission is the spread of viruses from the upper leaves to the lower leaves of the plant, and horizontal transmission is the spread of a virus among leaves at the same general level. C) Vertical transmission is the spread of viruses from trees and tall plants to bushes and other smaller plants, and horizontal transmission is the spread of viruses among plants of similar size. D) Vertical transmission is the transfer of DNA from one type of plant virus to another, and horizontal transmission is the exchange of DNA between two plant viruses of the same type.

A) Vertical transmission is transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant.

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

B) It uses viral RNA as a template for DNA synthesis.

Why do RNA viruses tend to have unusually high rates of mutation? A) RNA nucleotides are more unstable than DNA nucleotides. B) Replication of their genomes does not involve correcting errors in genome replication. C) RNA viruses replicate faster. D) RNA viruses can incorporate a variety of nonstandard bases.

B) Replication of their genomes does not involve correcting errors in genome replication.

Which of the following responses correctly lists the order of events in a generalized viral replicative cycle? A) Enzymes transcribe the viral genome into mRNA, the virus enters the cell, host enzymes replicate the viral genome. B) The virus enters the cell, host enzymes replicate the viral genome, enzymes transcribe the viral genome into mRNA. C) Host enzymes replicate the viral genome, enzymes transcribe the viral genome into mRNA, the virus enters the cell. D) The virus enters the cell, enzymes transcribe the viral genome into mRNA, host enzymes replicate the viral genome.

B) The virus enters the cell, host enzymes replicate the viral genome, enzymes transcribe the viral genome into mRNA.

Which of the following statements accurately describes plant virus infections? A) They can be controlled by the use of antibiotics. B) They are spread via the plasmodesmata. C) They have little effect on plant growth. D) They are rarely spread by insects.

B) They are spread via the plasmodesmata

Which of the following statements correctly describes adenoviruses? A) They contain RNA surrounded by a capsid. B) They contain DNA surrounded by a capsid. C) They contain RNA surrounded by a membranous envelope. D) They are a type of bacteriophage.

B) They contain DNA surrounded by a capsid.

How do antiviral drugs help to treat viral infections? A) They remove all viruses from the infected host. B) They interfere with viral replication. C) They remove all viral proteins from the host. D) They remove all viral mRNAs from the host.

B) They interfere with viral replication.

Which of the following processes can be effective in preventing the onset of viral infection in humans? A) taking vitamins B) getting vaccinated C) taking antibiotics D) applying antiseptics

B) getting vaccinated

The herpesviruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters. Some of the human ones 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 then reactivate, replicate again, and be infectious to others. If scientists are trying to use what they know about HSV to devise a means of protecting other people from being infected, which of the following would have the best chance of lowering the number of new cases of infection? A) vaccination of all persons with preexisting cases B) interference with new viral replication in preexisting cases C) treatment of the HSV lesions to shorten the breakout D) medication that destroys surface HSV before it gets to neurons

B) interference with new viral replication in preexisting cases

You isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, or prion. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. I.​Treat the substance with nucleases that destroy all nucleic acids and then determine whether it is still infectious. II.​Filter the substance to remove all elements smaller than what can be easily seen under a light microscope. III.​Culture the substance by itself on nutritive medium, away from any plant cells. IV.​Treat the sample with proteases that digest all proteins and then determine whether it is still infectious. If you already knew that the infectious agent was a prion, which treatment listed above would allow you to distinguish this? A) I only B) II only C) III only D) either I or IV

C) III only

Which of the following statements correctly 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 replicates along with the host genome. D) Certain environmental triggers can cause the phage to exit the host genome, switching from the lytic to the lysogenic.

C) The phage genome replicates along with the host genome.

A researcher lyses a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur? A) The plants would develop some but not all of the symptoms of the TMV infection. B) The plants would develop symptoms typically produced by viroids. C) The plants would develop the typical symptoms of TMV infection. D) The plants would not show any disease symptoms.

C) The plants would develop the typical symptoms of TMV infection.

A human pandemic is A) a viral disease that infects all humans. B) a flu that kills more than 1 million people. C) an epidemic that extends around the world. D) a virus that increases in mortality rate as it spreads.

C) an epidemic that extends around the world.

Which of the following characteristics, structures, or processes is common to both bacteria and viruses? A) metabolism B) ribosomes C) genetic material composed of nucleic acid D) cell division

C) genetic material composed of nucleic acid

In the figure above, 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

C) host cell DNA polymerase

Which of the following statements correctly describes one characteristic of the lytic cycle of viral replication? A) Many bacterial cells containing viral DNA are produced. B) Viral DNA is incorporated into the host genome. C) The viral genome replicates without destroying the host. D) A large number of phages are released at a time.

D) A large number of phages are released at a time.

Which of the following series of events best reflects what we know about how the flu virus moves between species? A) An avian flu virus undergoes several mutations and rearrangements such that it is able to be transmitted to other birds and then to humans. B) The flu virus in a pig is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected. C) A flu virus from a human epidemic or pandemic infects birds; the birds replicate the virus differently and then pass it back to humans. D) An animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates and is passed to a new species such as a bird, and the virus mutates and can be transmitted to humans.

D) An animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates and is passed to a new species such as a bird, and the virus mutates and can be transmitted to humans.

Which of the following nucleic acids make(s) up viral genomes? A) double-stranded RNA only B) DNA only C) single-stranded RNA only D) DNA or RNA

D) DNA or RNA

Which of the three types of viruses shown in the figure above would you expect to include glycoproteins as part of their overall structure? A) I only B) II only C) III only D) I and II only

D) I and II only

A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced would have A) T2 protein and T4 DNA. B) T4 protein and T2 DNA. C) T2 protein and T2 DNA. D) T4 protein and T4 DNA.

D) T4 protein and T4 DNA.

Which of the following statements correctly describes the most probable fate of a newly emerging virus that causes high mortality in its host? A) It is able to spread to a large number of new hosts quickly because the new hosts have no immunological memory of them. B) The new virus replicates quickly and undergoes rapid adaptation to a series of divergent hosts. C) Sporadic outbreaks will be followed almost immediately by a widespread pandemic. D) The newly emerging virus will die out rather quickly or will mutate to be far less lethal.

D) The newly emerging virus will die out rather quickly or will mutate to be far less lethal.

The herpesviruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters. Some of the human ones 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 then reactivate, replicate again, and be infectious to 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 describes 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 it is injected like the genome of a phage. D) The viral envelope mediates entry into the cell, the capsid docks onto the nuclear membrane, and the genome is all that enters the nucleus.

D) The viral envelope mediates entry into the cell, the capsid docks onto the nuclear membrane, and the genome is all that enters the nucleus.

Which of the following statements correctly describes viruses? A) They cannot reproduce without a host cell. B) They can reproduce by dividing. C) They can carry out their own metabolic activities. D) They have a genome similar to prokaryotic and eukaryotic cells.

D) They have a genome similar to prokaryotic and eukaryotic cells.

Some people who have had a herpesvirus-mediated cold sore or genital sore may have flare-ups for the rest of their life. Why does this occur? A) re-infection by a closely related herpesvirus of a different strain B) re-infection by the same herpesvirus strain C) co-infection with an unrelated virus that causes the same symptoms D) copies of the herpesvirus genome remaining as mini-chromosomes in some host cell nuclei

D) copies of the herpesvirus genome remaining as mini-chromosomes in some host cell nuclei

Which viruses have single-stranded RNA that acts as a template for DNA synthesis? A) lytic phages B) proviruses C) viroids D) retroviruses

D) retroviruses

In the figure above, when new viruses are being assembled during the step labeled IV, how is the assembly of the new virus particles completed? A) by host cell chaperones B) by assembly proteins coded for by the host nucleus C) by assembly proteins coded for by the viral genes D) the proteins self-assemble

D) the proteins self-assemble