7.3.E: Viruses (Exercises)
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- Ying Liu
- City College of San Francisco
These are homework exercises to accompany Kaiser's "Microbiology" TextMap. Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell (unicellular), cell clusters or no cell at all (acellular). This includes eukaryotes, such as fungi and protists, and prokaryotes. Viruses and prions, though not strictly classed as living organisms, are also studied.
10.1: General Characteristics of Viruses
Study the material in this section and then write out the answers to these questions. Do not just click on the answers and write them out. This will not test your understanding of this tutorial.
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State 2 living characteristics of viruses.
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State 2 nonliving characteristics of viruses.
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List 3 criteria used to define a virus.
- A virus that infects only bacteria is termed a ___________________.
- State why viruses can't replicate on environmental surfaces or in synthetic laboratory medium.
10.2: Size and Shapes of Viruses
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- Compare the size of most viruses to that of bacteria.
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List 4 shapes of viruses.
10.3: Viral Structure
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- Briefly describe the structure of most viruses that infect humans.
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Define the following:
- capsid
- capsomeres
- nucleocapsid
- Describe how most animal viruses obtain their envelope.
- State why some bacteriophages are more complex than typical polyhedral or helical viruses.
10.4: Classification of Viruses
10.5: Other Acellular Infectious Agents: Viroids and Prions
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- Small, circular, single-stranded molecules of infectious that cause of a few plant diseases such as potato spindle-tuber disease,cucumber pale fruit, citrus exocortis disease, and cadang-cadang (coconuts) are called ____________.
- Infectious protein particlesthought to be responsible for a group of transmissible and/or inherited neurodegenerative diseases including Creutzfeldt-Jakob disease, kuru, and Gerstmann-Straussler- syndrome in humans as well as scrapie in sheep and goats are called ______________.
- Name 3 other neurological protein misfolding diseases that apprear to be initiated by prions.
10.6: Animal Virus Life Cycles
10.6A: The Productive Life Cycle of Animal Viruses
10.6B: Productive Life Cycle with Possible Latency
10.6C: The Life Cycle of HIV
10.6D: Natural History of a Typical HIV Infection
10.6E: The Role of Viruses in Tumor Production
10.7: Bacteriophage Life Cycles: An Overview
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Name the 2 types of bacteriophage life cycles and state what the bacteriophage capable of each is called.
10.7A: The Lytic Life Cycle of Bacteriophages
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Describethe 5 steps involved in the lytic life cycle of bacteriophages.
10.7B: The Lysogenic Life Cycle of Bacteriophages
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- Describehow the lysogenic life cycle of temperate bacteriophages differs from the lytic life cycle of lytic bacteriophages.
- What is spontaneous induction as it relates to the lysogenic life cycle?
- When a bacteriophage inserts its DNA into the DNA of the host bacterium, this form of the virus is called a ________________.
- The host bacterium for a bacteriophage is called a ________________.
- A virus capable of the lysogenic life cycle is called a __________________.
10.8: Pathogenicity of Animal Viruses
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Briefly describe 4 ways viruses can damage infected host cells.
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Briefly describe 2 different ways viruses can evade host immune defenses and give an example of a virus that uses each mechanism.
10.9: Bacteriophage-Induced Alterations of Bacteria
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- Describe how a bacteriophage may in some cases enable a bacterium to become virulent and state 2 examples.
10.10: Antiviral Agents
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- Explain why the antibiotics we use to treat bacterial infections are not effective against viral infections.
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Match the following drugs with the viral infections they are used against:
_____ amantadine, rimantidine, zanamivar, and oseltamivir
_____ acyclovir, famciclovir, penciclovir, and valacyclovir
_____ foscarnet, gancyclovir, cidofovir, valganciclovir, and fomivirsen
_____ AZT (ZDV), didanosine, zalcitabine, stavudine, nevirapine, delavirdine, saquinavir, and ritonavir
- HIV infection and AIDS
- influenza A
- severe CMV infections such as retinitis
- HSV and VZV infections
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Match the following:
_____ These are drugs that bind to the active site of an HIV-encoded protease and prevent it from cleaving the long gag-pol polyprotein and the gag polyprotein into essential proteins essential to the structure of HIV and to RNA packaging within its nucleocapsid. As a result, viral maturation does not occur and noninfectious viral particles are produced.
_____ These drugs chemically resemble normal DNA nucleotides, the building block molecules for DNA synthesis. They bind to the active site of the reverse transcriptase which, in turn, inserts it into the growing DNA strand in place of a normal nucleotide. Once inserted, however, new DNA nucleotides are unable to attach to the drug and DNA synthesis is stopped. This results in an incomplete provirus.
- nucleoside reverse transcriptase inhibitors
- non-nucleoside reverse transcriptase inhibitors
- protease inhibitors
- entry inhibitors
10.11: General Categories of Viral Infections
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Match the following:
_____ Viral infections in which the infectious agents gradually increase in number over a very long period of time during which no significant symptoms are seen.
_____ Viral infections of relatively short duration with rapid recovery.
_____ Viral infections where the virus can be demonstrated in the body at all times and the disease may be present or absent for an extended period of time.
_____ Viral infections where the virus remains in equilibrium with the host for long periods of time before symptoms again appear, but the actual viruses cannot be detected until reactivation of the disease occurs.
- acute viral infection
- chronic viral infection
- latent viral infection
- slow viral infection
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Give an example of of a virus causing each of the following:
- acute viral infection
- chronic viral infection
- latent viral infection
- slow viral infection