Info

1. For each pair of terms, explain how the meanings of the terms differ.

a. virus and viroid b. oncogene and proto-oncogene c. capsid and envelope d. provirus and vector

2. Use the following terms in the same sentence: virus, lytic cycle, lysogenic cycle, and bacteriophage.

3. Use each of the following terms in a separate sentence: prion, prophage, temperate virus, and bacteriophage.

4. Word Roots and Origins The word virus is derived from the Greek ios, which means "poison." Using this information, explain why the term virus is a good name for these particles.

Understanding Key Concepts

5. Summarize how the structure of viruses was discovered by Wendell Stanley.

6. Discuss why viruses are not considered living organisms.

7. Describe three different shapes viruses can have.

8. Compare replication in DNA viruses to replication in RNA viruses.

9. Differentiate the lytic cycle of viral replication from the lysogenic cycle of viral replication in bacteriophages.

10. Summarize how viruses are thought to have originated.

11. Describe four diseases caused by viruses that occur in humans.

12. Name three vectors of viral diseases that can spread viruses to humans.

13. Discuss the role of viruses and oncogenes in the onset of cancer.

14. Describe the structure of HIV.

15. Explain the activity of reverse transcriptase in the replication cycle of the human immunodeficiency virus (HIV).

16. Summarize how emerging diseases can occur.

17. Discuss three methods humans use to control the spread of viral diseases.

18. Describe how viruses, viroids, and prions differ from one another.

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CONCEPT MAPPING Use the following terms to create a concept map that describes the lytic cycle: viruses, virulent, phage, injects, DNA, replicates, assemble, protein, and lyse.

Critical Thinking

20. Evaluating Information The drug azidothymidine (AZT) works by blocking the enzyme reverse transcriptase. Explain how AZT can help patients infected with HIV.

21. Applying Information Shingles is a disease caused by the same herpesvirus that causes chickenpox. How do you account for the fact that shingles often appears years after the initial chickenpox attack?

22. Applying Current Research Based on your knowledge of HIV structure and replication, describe one way to interrupt the replication of HIV.

23. Applying Information How does the increase of resistance to antiviral drugs in HIV relate to the theory of evolution by natural selection?

24. Applying Information Tobacco mosaic virus does not infect humans, but humans can transmit TMV from infected plants to healthy plants. What role do humans play in this mode of transmission?

25. Making Real-Life Connections For viral diseases without known cures, such as AIDS, certain types of hepatitis, and Ebola, identify ways in which the incidence of such diseases can be reduced.

26. Interpreting Graphics Look at the graph below. Discuss how the sharp jump in the number of viruses outside the cell corresponds to the phases of the lytic cycle.

Growth Curve of Viruses

Time

y1 1

<¿9 Standardized Test Preparation

DIRECTIONS: Choose the letter of the answer choice that best answers the question.

1. What are viruses made of?

A. enzymes and fats

B. carbohydrates and ATP

C. protein and nucleic acids

D. mitochondria and lysosomes

2. How do viroids differ from viruses?

F. Viroids are larger in size.

G. Viroids do not have a capsid.

H. Viroids do not have nucleic acids. J. Viroids can cause disease in plants.

3. During which of the following processes does a phage kill its host?

A. conjugation

B. transcription

C. the lytic cycle

D. the lysogenic cycle

4. Which of the following is one reason why viruses are not considered living organisms?

F. Viruses are able to grow.

G. Viruses do not metabolize.

H. Viruses can reproduce by splitting.

J. Viruses are too small to be easily observed.

INTERPRETING GRAPHICS: Study the figure below to answer the following questions.

5. Which of the following does the diagram represent?

A. a virus

B. a prion

C. a viroid

D. a bacterium

6. To which of the following is label X pointing?

F. envelope

G. nucleic acid

H. protein coat

J. cell membrane

DIRECTIONS: Complete the following analogy.

A. virus

B. insect

C. fungus

D. bacterium

INTERPRETING GRAPHICS: The figure below represents the human immunodeficiency virus. Use the figure to answer the question that follows.

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