Concept Questions

Take some time to write answers to these questions. If you can answer them, you have a good grasp of the material!

1. Describe 10 unique characteristics of viruses (can include structure, behavior, multiplication). After consulting table 6.2, what additional statements can you make about viruses, especially as compared with cells?

2. What does it mean to be an obligate intracellular parasite? What is another way to describe the sort of parasitism exhibited by viruses?

3. Characterize the viruses according to size range. What does it mean to say that they are ultramicroscopic? That they are filterable?

4. Describe the general structure of viruses. What is the capsid, and what is its function? How are the two types of capsids constructed? What is a nucleocapsid? Give examples of viruses with the two capsid types. What is an enveloped virus, and how does the envelope arise? Give an example of a common enveloped human virus. What are spikes, how are they formed, and what is their function?

5. What are bacteriophages, and what is their structure? What is a tobacco mosaic virus? How are the poxviruses different from other animal viruses?

6. Since viruses lack metabolic enzymes, how can they synthesize necessary components? What are some enzymes with which the virus is equipped?

7. How are viruses classified? What are virus families? How are generic and common names used? Looking at table 6.3, how many different viral diseases can you count?

8. Compare and contrast the main phases in the lytic multiplication cycle in bacteriophages and animal viruses. When is a virus a virion? What is necessary for adsorption? Why is penetration so different in the two groups? What is eclipse? In simple terms, what does the virus nucleic acid do once it gets into the cell? What is involved in assembly?

9. What is a prophage or temperate phage? What is lysogeny?

10. What dictates the host range of animal viruses? What are two ways that animal viruses penetrate the host cell? What is uncoating?

11. Describe the two ways that animal viruses leave their host cell.

12. Describe several cytopathic effects of viruses. What causes the appearance of the host cell? How might it be used to diagnose viral infection?

13. What does it mean for a virus to be persistent or latent, and how are these events important? Briefly describe the action of an oncogenic virus.

14. Describe the three main techniques for cultivating viruses. What is the advantage of using cell culture? The disadvantages? What is a disadvantage of using live intact animals or embryos? What is a cell line? A monolayer? How are plaques formed?

15. What is the principal effect of the agent of Creutzfeldt-Jakob disease? How is the agent different from viruses? What is a viroid? Why are virus diseases more difficult to treat than bacterial diseases?

16. Circle the viral infections from this list: cholera, rabies, plague, cold sores, whooping cough, tetanus, genital warts, gonorrhea, mumps, Rocky Mountain spotted fever, syphilis, rubella, rat bite fever.

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