front 1 3) Which of the following supports the argument that viruses are nonliving? A) They are not cellular. D) They do not evolve. | back 1 Answer: A |
front 2 4) Viruses _____. D) metabolize food and produce their own ATP | back 2 Answer: B |
front 3 5) What is the main structural difference between enveloped and
nonenveloped viruses? B) Nonenveloped viruses have only a phospholipid membrane, while
enveloped viruses have two membranes, the other one being a protein
capsid. | back 3 Answer: C |
front 4 6) The host range of a virus is determined by _____. A) the enzymes carried by the virus D) the proteins on its surface and that of the host | back 4 Answer: D |
front 5 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 | back 5 Answer: C |
front 6 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? B) positive control mechanisms rather than negative C) control of more than one gene in an operon | back 6 Answer: C |
front 7 9) Which of the following is characteristic of the lytic cycle? A) Viral DNA is incorporated into the host genome. C) A large number of phages are released at a time. D) The virus—host relationship usually lasts for generations. | back 7 Answer: C |
front 8 10) Which of the following statements 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. C) The phage genome replicates along with the host genome. D) The phage DNA is copied and exits the cell as a phage. | back 8 Answer: C |
front 9 11) Which viruses have single-stranded RNA that acts as a template for DNA synthesis? A) proviruses D) retroviruses | back 9 Answer: D |
front 10 12) What is the function of reverse transcriptase in retroviruses? A) It uses viral RNA as a template for DNA synthesis. D) It uses viral RNA as a template for making complementary RNA strands. | back 10 Answer: A |
front 11 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 6300 nucleotides. Its capsid is 25-30 nm in diameter and contains 180 identical capsomeres. 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 | back 11 Answer: C |
front 12 The herpes viruses 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. 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? 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. 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. | back 12 Answer: D |
front 13 17) 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 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? A) Host cell ribosomes only translate the viral code into short
polypeptides. | back 13 Answer: B |
front 14 20) The virus genome and viral proteins are assembled into virions
(virus particles) during _____. C) the lytic cycle only | back 14 Answer: C |
front 15 21) Which of the following viruses would most likely have reverse transcriptase? A) an RNA-based lytic virus D) a DNA-based lysogenic virus | back 15 Answer: B |
front 16 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? B) The viral capsid proteins would not be glycosylated and might not
arrive at the host plasma membrane. D) The virus would be unable to reproduce within the host cell. | back 16 Answer: A |
front 17 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 D) Disinfecting surfaces is more important to reduce the spread of HIV than the flu | back 17 Answer: B |
front 18 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? A) The virus causes mutations in the human cells, resulting in the
formation of new enzymes that are capable of performing these
roles. D) Viruses can stay in a quiescent state until the host cell evolves this ability. | back 18 Answer: B |
front 19 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 | back 19 Answer: C |
front 20 26) A virus consisting of a single strand of RNA, which is
transcribed into complementary DNA, is a _____. C) RNA replicase virus | back 20 Answer: B |
front 21 27) Which of the following could use reverse transcriptase to transcribe its genome? A) ssRNA D) dsDNA | back 21 Answer: A |
front 22 28) To make a vaccine against mumps, measles, or rabies, which type
of viruses would be useful? C) positive-sense ssRNA viruses | back 22 Answer: B |
front 23 29) Which of the following human diseases is caused by a virus that
requires reverse transcriptase to transcribe its genome inside the
host cell? C) smallpox | back 23 Answer: B |
front 24 30) Why do RNA viruses appear to have higher rates of mutation? A) RNA nucleotides are more unstable than DNA nucleotides. C) RNA viruses can incorporate a variety of nonstandard bases. D) RNA viruses are more sensitive to mutagens. | back 24 Answer: B |
front 25 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
_____. | back 25 Answer: B |
front 26 32) Which of the following can be effective in preventing the onset of viral infection in humans? A) taking vitamins D) taking drugs that inhibit transcription | back 26 Answer: B |
front 27 33) Viral infections in plants _____. | back 27 Answer: B |
front 28 34) Which of the following represents a difference between viruses
and viroids? D) Viruses cannot pass through plasmodesmata, whereas viroids can. | back 28 Answer: B |
front 29 35) The difference between vertical and horizontal transmission of
plant viruses is that vertical transmission is _____. B) the spread of viruses from upper leaves to lower leaves of the
plant, and horizontal transmission is the spread of a virus among
leaves at the same general level D) the transfer of DNA from a plant of one species to a plant of a different species, and horizontal transmission is the spread of viruses among plants of the same species | back 29 Answer: A |
front 30 36) What are prions? D) misfolded versions of normal protein that can cause disease | back 30 Answer: D |
front 31 37) A person is most likely to recover from a viral infection if the infected cells _____. A) can undergo normal cell division D) transcribe viral mRNA | back 31 Answer: A |
front 32 38) Effective antiviral drugs are usually associated with which of the following properties? A) interference with viral replication D) removal of viral mRNAs | back 32 Answer: A |
front 33 39) Which of the following best reflects what we know about how the
flu virus moves between species? B) 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, the virus is passed to a new species such as a bird, and the virus mutates again and can now be transmitted to humans. | back 33 Answer: D |
front 34 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. III. Culture the substance on nutritive medium, away from any plant
cells. 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 | back 34 Answer: C |
front 35 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. III. Culture the substance on nutritive medium, away from any plant
cells. 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? C) IV only | back 35 Answer: D |
front 36 The herpes viruses 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. 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? | back 36 Answer: B |
front 37 43) What is difference between an epidemic and a pandemic? | back 37 Answer: B |
front 38 44) Will treating a viral infection with antibiotics affect the
course of the infection? | back 38 Answer: A |
front 39 45) Why do scientists consider HIV to be an emerging virus? B) HIV mutates rapidly making the virus very different from HIV in
the early 1980s. | back 39 Answer: C |
front 40 46) A population of viruses with similar characteristics is called a _____. A) strain D) genome | back 40 Answer: A |
front 41 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? | back 41 Answer: D |
front 42 48) Which of the following processes within viral replication is the
greatest source of genetic variation in RNA virus populations? C) Capsid proteins from the host cell can replace the viral capsid. D) Viral RNA is translated by host cell ribosomes. | back 42 Answer: A |
front 43 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? A) The virus was descended from a common ancestor of bird, pig, and human flu viruses. B) The infected individuals happened to be infected with all three
virus types. D) The human was likely infected with various bacterial strains that contained all three RNA viruses. | back 43 Answer: C |