Test
Chapter 19
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Preguntas del test (40)
1
True or False: Martinus Beijernick gave the first credible evidence for the existence of a virus in the late 1800s and is credited with developing the concept of a virus.- AVerdadero
- BFalso
2The tobacco mosaic virus can be crystallized like many other biological molecules, organelles and cells.
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3Phages are animal specific viruses and do not infect plants.
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4The virus host range can be narrow or broad such as measles and influenza, respectively.
- AVerdadero
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5Viral RNA polymerase has no proof-reading activity and thus RNA viruses have a higher mutation rate than other viruses.
- AVerdadero
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6Once the components or parts of a virus are separated, they can not be assembled either inside or outside the host cell.
- AVerdadero
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7Bacterial restriction enzymes must be carefully deployed to deal with foreign DNA because they can also affect bacterial DNA.
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8Prophages integrate into the host's chromosomal DNA.
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9T4 phage is an example of a lysogenic bacteriophage and lambda page is an example of a lytic bacteriophage period.
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10 Bacteriophages provide a mechanism for introducing potentially deadly toxins into disease causing bacteria in humans.
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11Reversed transcriptase is found in host plant and animal cells.
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12Scientists have been unable to determine whether viruses first emerged or cells preceded them.
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13The influenza virus contains just one protein called hemagglutinin which helps it enter target cells.
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14Viroids are circular RNA molecules that infect animal cells only.
- AVerdadero
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15Prion mediated diseases have short incubation periods
- AVerdadero
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16
Which of the following supports the argument that viruses are nonliving?- AThey are not cellular.
- BTheir DNA does not encode proteins.
- CThey have RNA rather than DNA.
- DThey do not evolve.
17
What is the main structural difference between enveloped and nonenveloped viruses?- AEnveloped viruses have their genetic material enclosed by a layer made only of protein.
- BNonenveloped viruses have only a phospholipid membrane, while enveloped viruses have two membranes, the other one being a protein capsid.
- CEnveloped viruses have a phospholipid membrane outside their capsid, whereas nonenveloped viruses do not have a phospholipid membrane.
- DBoth types of viruses have a capsid and phospholipid membrane; but in the nonenveloped virus the genetic material is between these two membranes, while in the enveloped virus the genetic material is inside both membranes.
18
The host range of a virus is determined by _____.- Athe enzymes carried by the virus
- Bwhether its nucleic acid is DNA or RNA
- Cthe proteins on its surface and that of the host
- Dthe proteins in the host's cytoplasm
19
Which of the following accounts for someone who has had regular herpesvirus-mediated cold sore or genital sore flare-ups?- Are-infection by a closely related herpesvirus of a different strain
- Bcopies of the herpesvirus genome are permanently maintained in host cell cytoplasm
- Ccopies of the herpesvirus genome are permanently maintained in host nuclei
- Dre-infection by the same herpesvirus strain
20Which of the following is characteristic of the lytic cycle?
- AViral DNA is incorporated into the host genome.
- BThe viral genome replicates without destroying the host.
- CA large number of phages are released at a time.
- DThe virus-host relationship usually lasts for generations.
21Which of the following statements describes the lysogenic cycle of lambda (λ) phage?
- AAfter infection, the viral genes immediately turn the host cell into a lambda-producing factory, and the host cell then lyses.
- BMost of the prophage genes are activated by the product of a particular prophage gene.
- CThe phage genome replicates along with the host genome.
- DThe phage DNA is copied and exits the cell as a phage.
22
Which viruses have single-stranded RNA that acts as a template for DNA synthesis?- Aproviruses
- Bviroids
- Cbacteriophages
- Dretroviruses
23What is the function of reverse transcriptase in retroviruses?
- AIt uses viral RNA as a template for DNA synthesis.
- BIt converts host cell RNA into viral DNA.
- CIt translates viral RNA into proteins.
- DIt uses viral RNA as a template for making complementary RNA strands.
24
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 6,300 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?- Areplication rate
- Btranscription rate
- Ctranslation rate
- Dformation of new transcription factors
25
The virus genome and viral proteins are assembled into virions (virus particles) during _____.- Athe lytic cycle and the lysogenic cycle in all known host organisms
- Bthe lysogenic cycle only
- Cthe lytic cycle only
- Dthe lytic cycle in all host organisms but the lysogenic cycle only in bacteria
26
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?- AHIV can be transmitted more easily from person to person than the flu virus
- BThe flu virus can be transmitted more easily from person to person than HIV
- CThis property of HIV makes it more likely to be a pandemic than the flu virus
- DDisinfecting surfaces is more important to reduce the spread of HIV than the flu
27
The first class of drugs developed to treat AIDS, such as AZT, were known as reverse transcriptase inhibitors. They worked because they _____.- Atargeted and destroyed the viral genome before it could be reverse transcribed into DNA
- Bbonded to the dsDNA genome of the virus in such a way that it could not separate for replication to occur
- Cbonded to the viral reverse transcriptase enzyme, thus preventing the virus from making a DNA copy of its RNA genome
- Dprevented host cells from producing the enzymes used by the virus to replicate its genome
28
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 can expect that the plants would _____.- Adevelop some but not all of the symptoms of the TMV infection
- Bdevelop the typical symptoms of TMV infection
- Cnot show any disease symptoms
- Dbecome infected, but the sap from these plants would be unable to infect other plants
29
Which of the following can be effective in preventing the onset of viral infection in humans?- Ataking vitamins
- Bgetting vaccinated
- Ctaking antibiotics
- Dtaking drugs that inhibit transcription
30
Which of the following represents a difference between viruses and viroids?- AViruses infect many types of cells, whereas viroids infect only prokaryotic cells.
- BViruses have capsids composed of protein, whereas viroids have no capsids.
- CViruses have genomes composed of RNA, whereas viroids have genomes composed of DNA.
- DViruses cannot pass through plasmodesmata, whereas viroids can.
31
The difference between vertical and horizontal transmission of plant viruses is that vertical transmission is _____.- Atransmission of a virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant
- Bthe 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
- Cthe 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
- Dthe 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
32
What are prions?- Amobile segments of DNA
- Btiny circular molecules of RNA that can infect plants
- Cviral DNA that attaches itself to the host genome and causes disease
- Dmisfolded versions of normal protein that can cause disease
33
Which of the following best reflects what we know about how the flu virus moves between species?- AThe flu virus in a pig is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected.
- BA flu virus from a human epidemic or pandemic infects birds; the birds replicate the virus differently and then pass it back to humans.
- CAn influenza virus gains new sequences of DNA from another virus, such as a herpesvirus; this enables it to be transmitted to a human host.
- DAn 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.
34
Will treating a viral infection with antibiotics affect the course of the infection?- ANo; antibiotics work by inhibiting enzymes specific to bacteria. Antibiotics have no effect on eukaryotic or virally encoded enzymes.
- BNo; antibiotics do not kill viruses because viruses do not have DNA or RNA.
- CYes; antibiotics activate the immune system, and this decreases the severity of the infection.
- DYes; antibiotics can prevent viral entry into the cell by binding to host-receptor proteins.
35Which of the following processes within viral replication is the greatest source of genetic variation in RNA virus populations?
- AHigh mutation rate due to lack of proofreading of RNA genome replication errors.
- BTranscription from the host cell RNA polymerase introduces numerous mutations.
- CCapsid proteins from the host cell can replace the viral capsid.
- DViral RNA is translated by host cell ribosomes.
36
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?- AThe virus was descended from a common ancestor of bird, pig, and human flu viruses.
- BThe infected individuals happened to be infected with all three virus types.
- CRelated viruses can undergo genetic recombination if the RNA genomes mix and match during viral assembly.
- DThe human was likely infected with various bacterial strains that contained all three RNA viruses.
37
Effective antiviral drugs are usually associated with which of the following properties?- Ainterference with viral replication
- Bprevention of the host from becoming infected
- Cremoval of viral proteins
- Dremoval of viral mRNAs
38
A population of viruses with similar characteristics is called a _____.- Astrain
- Bspecies
- Ctype
- Dgenome
39Viral infections in plants _____.
- Acan be controlled with antibiotics
- Bcan spread within a plant via plasmodesmata
- Chave little effect on plant growth
- Dare not spread by animals
40
A virus consisting of a single strand of RNA, which is transcribed into complementary DNA, is a _____.- Aprotease
- Bretrovirus
- CRNA replicase virus
- Dnonenveloped virus
Información
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- Test sobre Chapter 19, creado por Lucy Dale el 07/05/2017.
- Autor
- Lucy Dale
- Idioma
- English
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