Chapter 19

38) Effective antiviral drugs are usually associated with which of the following properties?

A) interference with viral replication

4) Viruses _____.

B) use the host cell to copy themselves and make viral proteins

48) Which of the following processes within viral replication is the greatest source of genetic variation in RNA virus populations?

A) High mutation rate due to lack of proofreading of RNA genome replication errors.

12) What is the function of reverse transcriptase in retroviruses?

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

44) Will treating a viral infection with antibiotics affect the course of the infection?

A) No; antibiotics work by inhibiting enzymes specific to bacteria. Antibiotics have no effect on eukaryotic or virally encoded enzymes.

22) If a viral host cell has a mutation that interferes with the addition of carbohydrates to proteins in the Golgi, which of the following could likely result?

A) The viral envelope proteins would not be glycosylated and might not arrive at the host plasma membrane.

3) Which of the following supports the argument that viruses are nonliving?

A) They are not cellular.

37) A person is most likely to recover from a viral infection if the infected cells _____.

A) can undergo normal cell division

27) Which of the following could use reverse transcriptase to transcribe its genome?

A) ssRNA

46) A population of viruses with similar characteristics is called a _____.

A) strain

35) The difference between vertical and horizontal transmission of plant viruses is that vertical transmission is _____.

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

2) Which of the three types of viruses shown above would you expect to include a capsid(s)?

D) I, II, and III

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

B) AIDS

43) What is difference between an epidemic and a pandemic?

B) An epidemic is restricted to a local region; a pandemic is global.

30) Why do RNA viruses appear to have higher rates of mutation?

B) Replication of their genomes does not involve proofreading.

17) Poliovirus is an RNA virus of the picornavirus group, which uses its RNA as mRNA. At its end, the RNA genome has a viral protein (VPg) instead of a cap. This is followed by a nontranslated leader sequence, and then a single long protein-coding region (~7000 nucleotides), followed by a poly-A tail. Observations were made that used radioactive amino acid analogues. 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?

B) The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones.

23) HIV is inactivated in the laboratory after a few minutes of sitting at room temperature, but the flu virus is still active after sitting for several hours. What are the practical consequences of these findings?

B) The flu virus can be transmitted more easily from person to person than HIV

24) Viruses use the host's machinery to make copies of themselves. However, some human viruses require a type of replication that humans do not normally have. For example, humans normally do not have the ability to convert RNA into DNA. How can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires?

B) The viral genome codes for specialized enzymes not in the host.

34) Which of the following represents a difference between viruses and viroids?

B) Viruses have capsids composed of protein, whereas viroids have no capsids.

21) Which of the following viruses would most likely have reverse transcriptase?

B) an RNA-based lysogenic virus

33) Viral infections in plants _____.

B) can spread within a plant via plasmodesmata

31) 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. We expect that the plants would _____.

B) develop the typical symptoms of TMV infection

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

B) getting vaccinated

42) 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?

B) interfere with new viral replication in preexisting cases of HSV

28) To make a vaccine against mumps, measles, or rabies, which type of viruses would be useful?

B) negative-sense ssRNA viruses

26) A virus consisting of a single strand of RNA, which is transcribed into complementary DNA, is a _____.

B) retrovirus

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

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

18) Using the data in the figure above, how long does it take for virus A to go through one lytic cycle?

C) 45 minutes

9) Which of the following is characteristic of the lytic cycle?

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

5) What is the main structural difference between enveloped and nonenveloped viruses?

C) Enveloped viruses have a phospholipid membrane outside their capsid, whereas nonenveloped viruses do not have a phospholipid membrane.

45) Why do scientists consider HIV to be an emerging virus?

C) HIV suddenly became apparent and widespread in the 1980s.

You isolate an infectious substance capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal to analyze the substance and determine the nature of the infectious agent. I. Treat the substance with enzymes that destroy all nucleic acids and then determine whether the substance 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 on nutritive medium, away from any plant cells. IV. Treat the sample with proteases that digest all proteins and then determining whether thesubstance is still infectious. 40) If you already know that the infectious agent was either bacterial or viral, which method(s) listed above would allow you to distinguish between these two possibilities?

C) II or III

49) In 2009, a flu pandemic was believed to have originated when viral transmission occurred from pig to human, thereby earning the designation, "swine flu." Although pigs are thought to have been the breeding ground for the 2009 virus, sequences from bird, pig, and human viruses were all found within this newly identified virus. What is the most likely explanation of why this virus contained sequences from bird, pig, and human viruses?

C) Related viruses can undergo genetic recombination if the RNA genomes mix and match during viral assembly.

11) Which viruses have single-stranded RNA that acts as a template for DNA synthesis?

D) retroviruses

25) The first class of drugs developed to treat AIDS, such as AZT, were known as reverse transcriptase inhibitors. They worked because they _____.

C) bonded to the viral reverse transcriptase enzyme, thus preventing the virus from making a DNA copy of its RNA genome

8) 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 would you expect of the genes of a bacteriophage?

C) control of more than one gene in an operon

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

C) copies of the herpesvirus genome permanently maintained in host nuclei

13) In the figure, at the arrow marked II, what enzyme(s) are being utilized?

C) host cell DNA polymerase

20) The virus genome and viral proteins are assembled into virions (virus particles) during _____.

C) the lytic cycle only

15) 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?

C) translation rate

19) Using the data in the figure above, how long does it take for virus B to go through one lytic cycle?

D) 60 minutes

39) Which of the following best reflects what we know about how the flu virus moves between species?

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

1) Which of the three types of viruses shown above would you expect to include glycoproteins?

D) I and II only

47) Evidence suggests that factors which contribute towards the virulence of E. coli strain O157:H7, a bacterial strain reported to cause several food poisoning deaths, are caused by genes from a virus that infects bacteria. Considering this evidence, which statement most likely explains how the O157:H7 population acquired the genetic variation that distinguishes the strain from harmless E. coli strains, such as those that reside in our intestines?

D) The virus infected the bacterium, and allowed the bacterial population to replicate with a copy of the phage genome in each new bacterium.

16) 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 best fits these observations?

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.

41) If you already know that the infectious agent was either a viroid or a prion, which method(s) listed above would allow you to distinguish between these two possibilities?

D) either I or IV

36) What are prions?

D) misfolded versions of normal protein that can cause disease

14) In the figure, when new viruses are being assembled at the point marked IV, what mediates the assembly?

D) nothing; they self-assemble

6) The host range of a virus is determined by _____.

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