Biology Chapter 19
10) 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.
A) It uses viral RNA as a template for DNA synthesis.
24) 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. B) No; antibiotics do not kill viruses because viruses do not have DNA or RNA. C) Yes; antibiotics activate the immune system, and this decreases the severity of the infection. D) Yes; antibiotics can prevent viral entry into the cell by binding to host-receptor proteins.
A) No; antibiotics work by inhibiting enzymes specific to bacteria. Antibiotics have no effect on eukaryotic or virally encoded enzymes.
1) 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.
A) They do not carry out metabolic processes.
21) 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 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 C) 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) 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
A) transmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant
18) Why do RNA viruses appear to have higher rates of mutation? A) RNA nucleotides are more unstable than DNA nucleotides. B) Replication of their genomes does not involve proofreading. C) RNA viruses can incorporate a variety of nonstandard bases. D) RNA viruses are more sensitive to mutagens.
B) Replication of their genomes does not involve proofreading.
15) 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? A) HIV can be transmitted more easily from person to person than the flu virus. B) The flu virus can be transmitted more easily from person to person than HIV. C) This property of HIV makes it more likely to be a pandemic than the flu virus. D) Disinfecting surfaces is more important to reduce the spread of HIV than the flu.
B) The flu virus can be transmitted more easily from person to person than HIV.
19) 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. What would you expect to happen to the plants that were sprayed with the mixture? A) The plants would develop some but not all of the symptoms of the TMV infection. B) The plants would develop the typical symptoms of TMV infection. C) The plants would not show any disease symptoms. D) The plants would become infected, but extracts from these plants would be unable to infect other plants.
B) The plants would develop the typical symptoms of TMV infection.
16) Viruses use the host cell'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. B) The viral genome codes for specialized enzymes not found in the host cells. C) The virus infects only those cells and species that can perform all the replication roles necessary. D) Viruses can stay in a quiescent state until the host cell evolves this ability.
B) The viral genome codes for specialized enzymes not found in the host cells.
2) 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.
B) They can use the host cell to copy themselves and make viral proteins.
14) Which of the following viruses would most likely have reverse transcriptase inside them? A) an RNA-based lytic virus B) an RNA-based lysogenic virus C) a DNA-based lytic virus D) a DNA-based lysogenic virus
B) an RNA-based lysogenic virus
27) RNA viruses require their own supply of certain enzymes because A) host cells rapidly destroy the viruses. B) host cells lack enzymes that can replicate the viral genome. C) these enzymes translate viral mRNA into proteins. D) these enzymes penetrate host cell membranes.
B) host cells lack enzymes that can replicate the viral genome.
7) 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
C) A large number of phages are released at a time.
30) 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. C) Related viruses can undergo genetic recombination if the RNA genomes mix and match during viral assembly. D) The human was likely infected with various bacterial strains that contained all three RNA viruses.
C) Related viruses can undergo genetic recombination if the RNA genomes mix and match during viral assembly.
17) The first class of antiviral drugs developed to treat HIV infection, such as AZT, were known as reverse transcriptase inhibitors. How did these drugs carry out their functions? A) The drugs targeted and destroyed the viral genome before it could be reverse transcribed into DNA. B) The drug molecules bonded to the dsDNA genome of the virus in such a way that it could not separate for replication to occur. C) The drug molecules bonded to the viral reverse transcriptase enzyme, thus preventing the virus from making a DNA copy of its RNA genome. D) The drugs prevented host cells from producing the enzymes used by the virus to replicate its genome.
C) The drug molecules bonded to the viral reverse transcriptase enzyme, thus preventing the virus from making a DNA copy of its RNA genome.
8) 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.
C) The phage genome is integrated in the host chromosome where it is replicated along with the host genome.
3) 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.
C) Viruses with envelopes have a phospholipid membrane outside their capsid, whereas viruses without envelopes do not have a phospholipid membrane.
26) To cause a human pandemic, the H5N1 avian flu virus would have to A) spread to primates such as chimpanzees. B) develop into a virus with a different host range. C) become capable of human-to-human transmission. D) become much more pathogenic.
C) become capable of human-to-human transmission.
6) 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
C) control of more than one gene in an operon
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
C) copies of the herpesvirus genome permanently maintained in host nuclei
29) 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
13) 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
C) the lytic cycle only
23) Which of the following statements best reflects what we know about how the flu virus moves between species? A) The flu virus in a pig is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected. 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. C) An influenza virus gains new sequences of DNA from another virus, such as a herpesvirus; this enables it to be transmitted to a human host. 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.
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.
28) 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.
12) 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.
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
9) 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.
D) They have a single-stranded RNA that acts as a template for DNA synthesis.
20) Which of the following statements correctly describes a difference between viruses and prions? A) Viruses infect many types of cells, whereas prions infect only prokaryotic cells. B) Viruses have capsids composed of protein, whereas prions are made only of nucleic acid. C) Viruses have genomes composed of RNA, whereas prions have genomes composed of DNA. D) Viruses generally cause disease symptoms quickly, whereas prions generally take many years to cause disease symptoms.
D) Viruses generally cause disease symptoms quickly, whereas prions generally take many years to cause disease symptoms
25) Emerging viruses arise by A) mutation of existing viruses. B) the spread of existing viruses to new host species. C) the spread of existing viruses more widely within their host species. D) all of the above
D) all of the above
22) What are prions? A) mobile segments of DNA B) tiny circular molecules of RNA that can infect plants C) viral DNA that attaches itself to the host genome and causes disease D) misfolded versions of normal proteins that can cause disease
D) misfolded versions of normal proteins that can cause disease
11) Usually when new viruses are being assembled inside the host cell, 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
D) no mediator is required; the new viruses self-assemble
4) 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
D) the proteins on its surface and that of the host
