Chapter 13 Mastering Micro HW
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.
It is copied every time the host DNA replicates.
From which phrase is the term "prions" derived? Protein infections Protein infection of the nervous system Proteinaceous infectious particles Particles of infection
Proteinaceous infectious particles
Which of the following can be used directly as messenger RNA? +RNA -RNA ssDNA
+RNA
Which virus employs the use of an RNA-dependent RNA polymerase? dsDNA viruses +RNA viruses ssDNA viruses Retroviruses
+RNA viruses
In what year did Stanley Prusiner discover prions?
1982
Name the human disease caused by prions?
Creutzfeldt-Jakob disease (CJD)
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.
During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome.
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
Exposure to UV light
Viruses are the only known infectious agents that are obligatory intracellular parasites. True False
False
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.
Latent infections can persist for years in an individual without causing any symptoms.
How do normal prion proteins (PrP) differ from the infectious prion proteins?
Normal PrP have alpha-helices; infectious PrP have beta-pleated sheets.
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.
Normal host cellular prion proteins (PrPC) are converted into scrapie proteins (PrPSc).
How does the number of infectious prions increase?
Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion.
How are prions different from other infectious agents?
they lack nucleic acid
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.
Retroviruses use an enzyme called reverse transcriptase, which synthesizes DNA by copying RNA.
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.
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.
What occurs during viral uncoating? The viral proteins are synthesized. The viral envelope is released. The nucleic acid breaks apart, allowing for translation. The capsid breaks apart, releasing the viral genome.
The capsid breaks apart, releasing the viral genome.
How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?
The host cell dies during the lytic stage.
Why are the beta-pleated multimers of PrP potentially pathogenic
The multimers are more stable and resistant to protease.
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.
The virus would not be able to infect new hosts.
How do naked viruses differ from enveloped viruses in their attachment/penetration phase? Their DNA attaches to receptors on the cell surface. Their nucleic acids are injected into the cell. They uncoat after they enter the cell. Their protein coat fuses to the cell membrane.
Their nucleic acids are injected into the cell.
How are viruses different from cells? They require a host in order to reproduce. They do not contain enzymes. They do not contain genetic material. They do not contain protein.
They require a host in order to reproduce.
What is the function of the structural elements of a virus? To use all of the cell proteins To provide a source of energy for the virus To package and protect the viral genome
To package and protect the viral genome
Dogs do not get measles because their cells lack the correct receptor sites for that virus. True False
True
Which of the following statements about viruses is FALSE? Viruses use their own catabolic enzymes. Viruses have genes. Viruses contain DNA or RNA but never both. Viruses use the anabolic machinery of the cell. Viruses contain a protein coat.
Viruses use their own catabolic enzymes.
In which stage does formation of mature viruses occur?
assembly/maturation
The normal function of the PrP protein in mammals is believed to be:
assisting in normal synaptic development and function.
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? assembly uncoating attachment synthesis
attachment
The host DNA is usually degraded during which stage?
biosynthesis
Which virus is NOT associated with cancer? ANSWER: Epstein-Barr virus (EBV) coronavirus human papillomavirus (HPV) hepatitis B virus (HBV)
coronavirus
Which type of virus would produce viral glycoproteins to be expressed on the host cell membrane? +RNA viruses dsRNA viruses Naked viruses Enveloped viruses
enveloped viruses
In which stage is the viral DNA introduced into the cell?
penetration
Lysogenic viral DNA integrating into the host genome is referred to as
prophage
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? attachment release assembly synthesis
release
Which of the following viruses is transcribed from RNA to DNA to RNA during the replication cycle?
retroviruses
Which disease did Stanley Prusiner first identify as being caused by prions?
scrapie
