Chapter 13 Mastering Micro HW – Flashcards
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In what year did Stanley Prusiner discover prions?
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1982
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Which disease did Stanley Prusiner first identify as being caused by prions?
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scrapie
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How are prions different from other infectious agents?
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they lack nucleic acid
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Lysogenic viral DNA integrating into the host genome is referred to as
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prophage
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Which of the following events might trigger induction of a temperate bacteriophage? ANSWER: 1) Normal cell division of an infected cell 2) Bacterial conjugation 3) An infected cell entering the logarithmic phase of growth 4) Exposure to UV light
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Exposure to UV light
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How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?
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The host cell dies during the lytic stage.
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What is the fate of the prophage during the lysogenic stage? 1) It is packaged into viral proteins and maintained until the host is exposed to an environmental stress. 2) It is copied every time the host DNA replicates. 3) It is degraded by the activity of host defense enzymes. 4) It is released from the cell by lysing the cell.
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It is copied every time the host DNA replicates.
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How do naked viruses differ from enveloped viruses in their attachment/penetration phase?
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Their nucleic acids are injected into the cell.
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Which virus employs the use of an RNA-dependent RNA polymerase?
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+RNA viruses
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Which of the following viruses is transcribed from RNA to DNA to RNA during the replication cycle?
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retroviruses
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Which type of virus would produce viral glycoproteins to be expressed on the host cell membrane? +RNA viruses dsRNA viruses Naked viruses Enveloped viruses
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enveloped viruses
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Which of the following can be used directly as messenger RNA? +RNA -RNA ssDNA
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+RNA
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Which of the following statements concerning prion diseases is true? Normal host cellular prion proteins (PrPC) are converted into scrapie proteins (PrPSc). Prion diseases are always inherited. Prion diseases affect humans but not other animals. Prion diseases affect brain function but do not affect the morphology (overall appearance) of brain tissues.
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Normal host cellular prion proteins (PrPC) are converted into scrapie proteins (PrPSc).
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Which of the following statements concerning viruses is true? Viruses contain both DNA and RNA, and they undergo binary fusion. Viruses possess enzymes for protein synthesis and ATP generation. The "host range" for a virus is determined by the presence or absence of particular components on the surface of a host cell that are required for the virus to attach. Viruses are usually about the same size as bacteria.
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The "host range" for a virus is determined by the presence or absence of particular components on the surface of a host cell that are required for the virus to attach.
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In which stage is the viral DNA introduced into the cell?
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penetration
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In which stage does formation of mature viruses occur?
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assembly/maturation
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The host DNA is usually degraded during which stage?
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biosynthesis
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What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage? The virus would infect new hosts. The virus would not be able to infect new hosts. The cell could still be revived by the virus.
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The virus would not be able to infect new hosts.
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Name the human disease caused by prions?
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Creutzfeldt-Jakob disease (CJD)
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We sometimes are able to generate antibodies (immune system proteins) that bind to and cover up some of the proteins on the outermost portion of a virus while it is in the bloodstream. This renders the virus unable to reproduce. Which step of viral replication are antibodies directly preventing?
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attachment
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Enveloped viruses have a layer of lipids surrounding their capsid. This envelope is made mostly of host cell membrane. In which step does the virus acquire this envelope?
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release
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What occurs during viral uncoating?
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The capsid breaks apart, releasing the viral genome.
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Which of the following statements regarding latent viral infections is true? During latent infections, small amounts of virus are produced, and virus numbers build up over time. Latent infections can persist for years in an individual without causing any symptoms. Latent viral infections are caused by the slow conversion of cellular glycoproteins from normal to infectious form. Latent viral infections are almost always fatal.
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Latent infections can persist for years in an individual without causing any symptoms.
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Which statement is CORRECT concerning animal viruses? The genome of animal viruses is always single-stranded. Retroviruses use an enzyme called reverse transcriptase, which synthesizes DNA by copying RNA. Capsid proteins are produced in the nucleus. Enveloped viruses are surrounded by a lipid and carbohydrate coat, which is made from the host cell's mitochondria.
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Retroviruses use an enzyme called reverse transcriptase, which synthesizes DNA by copying RNA.
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Which of the following is true concerning a lysogenic viral replication cycle? ANSWER: Lysogenic infections are similar to persistent infections, in that virus is constantly produced. During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome. During lysogeny, the viral DNA is present as a circular plasmid. Once the lysogenic portion of the cycle has begun, virus is never produced again.
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During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome.
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Which virus is NOT associated with cancer? ANSWER: Epstein-Barr virus (EBV) coronavirus human papillomavirus (HPV) hepatitis B virus (HBV)
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coronavirus
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The normal function of the PrP protein in mammals is believed to be:
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assisting in normal synaptic development and function.
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How do normal prion proteins (PrP) differ from the infectious prion proteins?
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Normal PrP have alpha-helices; infectious PrP have beta-pleated sheets.
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How does the number of infectious prions increase?
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Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion.
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Why are the beta-pleated multimers of PrP potentially pathog
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The multimers are more stable and resistant to protease.
