micro ch 13 – Flashcards
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How do all viruses differ from bacteria?
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Viruses are not composed of cells.
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Which of the following statements provides the most significant support for the idea that viruses are nonliving chemicals?
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They cannot reproduce themselves outside a host.
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Which of the following statements about viral spikes is FALSE?
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They are found only on nonenveloped viruses.
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Which of the following is NOT used as a criterion to classify viruses?
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biochemical tests
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Which of the following is NOT utilized to culture viruses?
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culture media
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Bacteriophages and animal viruses do NOT differ significantly in which one of the following steps?
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biosynthesis
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The definition of lysogeny is
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phage DNA is incorporated into host cell DNA.
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A viroid is a(n)
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infectious piece of RNA without a capsid.
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A clear area against a confluent "lawn" bacteria is called a
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plaque.
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Continuous cell lines differ from primary cell lines in that
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continuous cell lines can be maintained through an indefinite number of generations.
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Which of the following is necessary for replication of a prion?
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PrPSc
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A persistent infection is one in which
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the disease process occurs gradually over a long period.
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Which of the following statements is FALSE?
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A) A prophage is phage DNA inserted into a bacterial chromosome.
B) A prophage can "pop" out of the chromosome.
C) Prophage genes are repressed by a repressor protein coded for by the prophage.
D) A prophage may result in new properties of the host cell.
E) The prophage makes the host cell immune to infection by other phages.
Answer: E
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Lysogeny can result in all of the following EXCEPT
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A) immunity to reinfection by the same phage.
B) acquisition of new characteristics by the host cell.
C) immunity to reinfection by any phage.
D) specialized transduction
E) phage conversion.
Answer: C
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Which of the following would be the first step in biosynthesis of a virus with a - (minus) strand of RNA?
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synthesis of double-stranded RNA from an RNA template
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An infectious protein is a
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prion
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An envelope is acquired during which of the following steps?
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release
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Which of the following statements is NOT true of lysogeny?
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A) It can give infected pathogens the genetic information for toxin production.
B) Prophage is inserted into the host genome.
C) Lytic cycle may follow lysogeny.
D) It is a "silent" infection; the virus does not replicate.
E) It causes lysis of host cells.
Answer: E
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An example of a latent viral infection is
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cold sores
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A virus' ability to infect an animal cell depends primarily upon the
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presence of receptor sites on the cell membrane.
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Assume you have isolated an unknown virus. This virus has a single, positive sense strand of RNA, and possesses an envelope. To which group does it most likely belong?
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togavirus
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The mechanism whereby an enveloped virus leaves a host cell is called
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budding
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The most conclusive evidence that viruses cause cancers is provided by
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cancer following injection of cell-free filtrates.
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Bacteriophages derive all of the following from the host cell EXCEPT
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A) lysozyme.
B) tRNA.
C) amino acids.
D) nucleotides.
E) ATP.
Answer: A
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Bacteriophage replication differs from animal virus replication because only bacteriophage replication involves
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injection of naked nucleic acid into the host cell.
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Generally, in an infection caused by a DNA-containing virus, the host animal cell supplies all of the following EXCEPT
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DNA polymerase.
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Which of the following places these items in the correct order for DNA-virus replication?
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1. DNA synthesis
2. Transcription
3. Translation
4. Maturation
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A viral species is a group of viruses that
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has the same genetic information and ecological niche.
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Viruses that utilize reverse transcriptase belong to the virus families
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Hepadnaviridae and Retroviridae.
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DNA made from an RNA template will be incorporated into the virus capsid of
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Hepadnaviridae.
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Which of the following statements about viruses is FALSE?
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Viruses use their own catabolic enzymes.
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A lytic virus has infected a patient. Which of the following would best describe what is happening inside the patient?
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The virus is causing the death of the infected cells in the patient.
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Some viruses, such as human herpesvirus 1, infect a cell without causing symptoms. These are called
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latent viruses
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The following steps occur during multiplication of herpesviruses. Which is the third step?
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uncoating
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The following steps occur during multiplication of retroviruses. Which is the fourth step?
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synthesis of double-stranded DNA
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Oncogenic viruses
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cause tumors to develop
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Which one of the following steps does NOT occur during multiplication of a picornavirus?
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synthesis of DNA
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Which of the following is most likely a product of an early gene?
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DNA polymerase
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Most RNA viruses carry which of the following enzymes?
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RNA-dependent RNA polymerase
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The following steps occur during biosynthesis of a + strand RNA virus. What is the third step?
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synthesis of - strand RNA
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What contributes to antigenic shift in influenza viruses?
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a segmented genome
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________ were first identified in cancer-causing viruses and can induce ________ in infected cells.
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Oncogenes; transformation
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The basic mechanism of viral multiplication is similar for all viruses.
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TRUE
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Positive sense RNA strands of viruses are treated like mRNA inside the host cell.
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TRUE
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Dogs do not get measles because their cells lack the correct receptor sites for that virus.
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TRUE
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A segmented genome can result in antigenic shift.
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TRUE
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Most drugs that interfere with viral multiplication also interfere with host cell function.
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TRUE
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A viroid is a completely developed infectious agent composed of nucleic acid and surrounded by a capsid.
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FALSE
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Binomial nomenclature is used to name viruses.
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FALSE
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Glycoprotein spikes are found on the capsids of all viruses.
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FALSE
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Helical and icosahedral are terms used to describe the shapes of a virus envelope.
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FALSE
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Viruses are the only known infectious agents that are obligatory intracellular parasites.
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FALSE
