Chapter 33 bio (1)
Which of the following human diseases is caused by a virus that requires reverse transcriptase to transcribe its genome inside the host cell? A) herpes B) AIDS C) smallpox D) influenza E) common cold
AIDS
It is believed that HIV has passed from chimps to humans more than once. This suggests that animal-to-human viral transmissions may be more common than previously thought. What is the best evidence in support of the conclusion that HIV made the chimp-to-human leap more than once? A) HIV has multiple strains, and the virus does not appear to be able to leap from humans back to chimps. B) HIV has appeared on multiple continents. C) Human-to-human transmission of HIV requires direct personal contact that simply could not have resulted in the widespread outbreak we see today. D) Several species are known to have similar viruses resulting in immunodeficiency diseases.
HIV has multiple strains, and the virus does not appear to be able to leap from humans back to chimps.
Viral envelopes can best be analyzed with which of the following techniques? A) use of 15N to label specific nucleotides B) antibodies against specific proteins not found in the host membranes C) DNA staining and visualization with the light microscope D) use of plaque assays for quantitative measurement of viral titer
antibodies against specific proteins not found in the host membranes
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 E) these enzymes cannot be made in host cells
host cells lack enzymes that can replicate the viral genome
Which of the following characteristics, structures, or processes is common to bacteria and viruses? A) metabolism B) ribosomes C) genetic material composed of nucleic acids D) cell division E) independent existence
genetic material composed of nucleic acids
Which of the following can be effective in preventing the onset of viral infection in humans? A) taking vitamins B) getting vaccinated C) taking antibiotics D) applying antiseptics E) taking drugs that inhibit transcription
getting vaccinated
When people die from HIV infections, it is usually because they ________. A) have too many HIV particles in their lymphatic system, which causes it to shut down B) have too few T cells to adequately fight infection C) have too many T cells, and this overwhelms their immune systems D) divert too much energy toward replicating the virus
have too few T cells to adequately fight infection
Effective antiviral drugs are usually associated with which of the following properties? A) ability to remove all viruses from the infected host B) interference with viral replication C) prevention of the host from becoming infected D) removal of viral proteins E) removal of viral mRNAs
interference with viral replication
the HIV protease has been the target of several anti-HIV medications called protease inhibitors. This antiviral strategy is possible because protease inhibitors ________. A) cause protease to precipitate out of the cell by combining with certain salt solutions B) cleave at specific places in viral polypeptides, resulting in the destruction of reverse transcriptase C) prevent HIV from generating ATP in the host cell D) prevent the formation of active viral proteins
prevent the formation of active viral proteins
Which viruses have single-stranded RNA that acts as a template for DNA synthesis? A) lytic phages B) proviruses C) viroids D) bacteriophages E) retroviruses
retroviruses
The virus genome and viral proteins are assembled into virions (virus particles) during ________. 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
the lyctic cycle only
In the figure, when new viruses are being assembled at the point marked IV, 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) viral RNA intermediates E) The viral components interact spontaneously and self assemble.
the viral components interact spontaneously and self assemble
You have isolated a newly discovered virus and are attempting to characterize it. You begin with its genome. You first isolate the virion-producing mRNA from cultured cells infected with the virus. When you compare this mRNA to the viral genome, you find that they are complementary. What does this tell you? A) This virus has a positive-sense genome. B) This virus has a negative-sense genome. C) This virus has an ambisense genome. D) The virus does not use DNA or RNA.
this virus has a negative-sense genome
Why do scientists consider HIV to be an emerging virus? A) HIV infected humans for many centuries. B) HIV mutates rapidly, making the virus very different from HIV in the early 1980s. C) HIV suddenly became apparent and widespread in the 1980s. D) HIV is now starting to cause diseases other than AIDS, such as rare types of cancers and pneumonias.
HIV suddenly became apparent and widespread in the 1980's
You believe that you have isolated a new strain of positive-sense, single-stranded RNA virus and set about studying it in your laboratory. Which of the following lines of evidence would most strongly support your hypothesis that the virus is a [+]ssRNA? A) The virions are diploid. B) You sequence the bases in the viral RNA and the mRNA and find them to be antiparallel. C) Introducing a protease inhibitor causes the virus to stop producing proteins and reproducing. D) Introducing a reverse transcriptase inhibitor slows down the growth of the virus.
Introducing a protease inhibitor causes the virus to stop producing proteins and reproducing.
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) T2 protein and T2 DNA. C) T4 protein and T4 DNA. D) T4 protein and T2 DNA.
T4 protein and T4 DNA
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 5' 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 results 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. B) The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones. C) The RNA is translated into short polypeptides, which are subsequently assembled into large ones. D) The large radioactive polypeptides are coded by the host, whereas the short ones are coded for by the virus.
The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones.
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. C)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) Only the genetic material of the virus is involved in the cell's infectivity, and is injected like the genome of a phage. E) The viral capsid mediates entry into the cell, and only the genomic DNA enters the nucleus, where it may or may not replicate.
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.
Which of the following viruses would most likely have reverse transcriptase? A) an RNA-based lytic virus B) an RNA-based lysogenic virus C) a DNA-based lytic virus D) a DNA-based lysogenic virus
an RNA-based lysogenic virus
What is the difference between an epidemic and a pandemic? A) An epidemic is a disease that spreads or becomes more common; a pandemic is a disease that remains stable in terms of numbers affected. B) An epidemic is a disease; a pandemic is a treatment. C) An epidemic is restricted to a local region; a pandemic is global. D) An epidemic has low mortality; a pandemic has higher mortality. E) An epidemic is caused by a bacterial infection; a pandemic is caused by a viral infection.
an epidemic is restricted to a local region; a pandemic is global
The first class of drugs developed to treat AIDS, such as AZT, were known as reverse transcriptase inhibitors. They worked because they ________. A) targeted and destroyed the viral genome before it could be reverse transcribed into DNA B) bonded to the dsDNA genome of the virus in such a way that it could not separate for replication to occur C) bonded to the viral reverse transcriptase enzyme, thus preventing the virus from making a DNA copy of its RNA genome D) prevented host cells from producing the enzymes used by the virus to replicate its genome
bonded to the viral reverse transcriptase enzyme, thus preventing the virus from making a DNA copy of its RNA genome
Mimivirus contains some of the genes required for protein synthesis. This is cited as support for which hypothesis about the origins of viruses? A) degeneration B) origin of life C) escaped-genes D) transposable elements
degeneration
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 ________. A) develop some but not all of the symptoms of the TMV infection B) develop symptoms typically produced by viroids C) develop the typical symptoms of TMV infection D) not show any disease symptoms E) become infected, but the sap from these plants would be unable to infect other plants
develop the typical symptoms of TMV infection
What is the main structural difference between enveloped and nonenveloped viruses? A) Enveloped viruses have their genetic material enclosed by a layer made only of protein. B) Nonenveloped viruses have only a phospholipid membrane, whereas enveloped viruses have two membranes, the other one being a protein capsid. C) Enveloped viruses have a phospholipid membrane outside their capsid, whereas nonenveloped viruses do not have a phospholipid membrane. D) Both types of viruses have a capsid and phospholipid membrane; but in the nonenveloped virus the genetic material is between these two membranes, and in the enveloped virus the genetic material is inside both membranes.
enveloped viruses have a phospholipid membrane outside their capsid, whereas nonenveloped viruses do not have a phospholipid membrane.
You just discovered a new virus. This virus infects heart muscle, where it causes inflammation, and has a very high mutation rate. Which of the following is the best strategy for finding a treatment for this virus? A) Develop a vaccine from living viruses. B) Identify the receptor this virus uses and develop an enzyme that blocks the receptor. C) Encourage infected individuals to engage in heart-strengthening exercise. D) Develop a drug that blocks the host's ribosomes, which the virus uses to produce its proteins.
identify the receptor this virus uses and develop an enzyme that blocks the receptor
You are a physician and you suspect your patient has a viral infection that has never been seen in humans. The infection is localized in the cells along the lining of the small intestine. The cells in this area are regularly sloughed off and replaced with new cells; that is, these cells are constantly dividing. When you isolate this new virus and incubate it in culture, you discover that it does not replicate well in cultures that have slowly dividing cells, but it does much more damage in cultures that have actively dividing cells. What do these findings suggest about this new virus? A) It is a double-stranded RNA virus. B) It is a negative-sense, single-stranded RNA virus. C) It is a double-stranded DNA virus. D) It is a single-stranded DNA virus.
it is a double-stranded DNA virus
You isolate a cell infected with an adenovirus. What are you most likely going to see when you examine the cell? A) It is a bacterium. B) It is undergoing mitosis. C) Reverse transcriptase is present in the nucleus. D) It does not have a nucleus.
it is undergoing mitosis
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 translates viral RNA into proteins. E) It uses viral RNA as a template for making complementary RNA strands
it uses viral RNA as a template for DNA synthesis
To make a vaccine against mumps, measles, or rabies, which type of viruses would be useful? A) dsDNA viruses B) negative-sense ssRNA viruses C) retroviruses D) positive-sense ssRNA viruses E) dsRNA viruses
negative sense ssRNA viruses
A biologist develops a new drug that seems to dramatically slow the onset of symptoms resulting from HIV infection. Close monitoring of HIV-infected cells reveals that the viral proteins are in the form of long polyproteins. The biologist most likely developed a ________. A) reverse transcriptase inhibitor B) CD4 inhibitor C) protease inhibitor D) polymerase inhibitor
protease inhibitor
A virus consisting of a single strand of RNA, which is transcribed into complementary DNA, is a ________. A) reverse transcriptase B) protease C) retrovirus D) RNA replicase virus E) nonenveloped virus
retrovirus
Which of the following could use reverse transcriptase to transcribe its genome? A) ssRNA B) dsRNA C) ssDNA D) dsDNA
ssRNA
A population of viruses with similar characteristics is called a ________. A) strain B) species C) type D) genome E) sense
strain
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 of the flu.
the flu virus can be transmitted more easily from person to person than HIV
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. B) The viral genome has genes coding for enzymes needed for its own reproduction. 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.
the viral genome has genes coding for enzymes needed for its own reproduction
What would the result be if a drug that blocks the action of RNA polymerase was introduced into a virus-infected organism? A) The virus would not be able to enter new host cells. B) The viral proteins would not be made and the virus would not be able to reproduce. C) The newly formed virions (virus particles) would be unable to leave the host cell. D) Viral proteins and viral DNA particles would not be able to assemble.
the viral proteins would not be made and the virus would not be able to reproduce.
Which of the following is characteristic of the lytic cycle? 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. E) The virus—host relationship usually lasts for generations.
the virus- host relationship usually lasts for generations
Which of the following supports the argument that viruses are nonliving? A) They lack genetic material. B) They are not cellular. C) Their DNA does not encode proteins. D) They have RNA rather than DNA. E) They do not evolve.
they are not cellular
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. 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? A) replication rate B) transcription rate C) translation rate D) accumulation of new ribosomes E) formation of new transcription factors
translation rate
Viruses ________. A) manufacture their own ATP, proteins, and nucleic acids B) use the host cell to copy themselves and make viral proteins C) use the host cell to copy themselves and then viruses synthesize their own proteins D) metabolize food and produce their own ATP
use the host cell to copy themselves and make viral proteins