Name Class Date. Infection in which a virus inserts its nucleic acid into the DNA of the host cell and is duplicated with the cell s DNA

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1 Name Class Date 20.1 Viruses Lesson Objectives Explain how viruses reproduce. Explain how viruses cause infection. BUILD Vocabulary A. The chart below shows key terms from the lesson with their definitions. Complete the chart by writing a strategy to help you remember the meaning of each term. One has been done for you. Term Definition Bacteriophage Capsid Infection in which a virus inserts its nucleic acid into the DNA of the host cell and is duplicated with the cell s DNA An infection in which a virus enters a bacterial cell, makes copies of itself, and causes the cell to burst, or lyse Prophage A virus that contains RNA as its genetic material and that copies its genetic material from RNA to DNA A nonliving particle made of proteins, nucleic acids, and sometimes lipids, that can only reproduce by infecting cells

2 The Discovery of Viruses Viruses are particles made up of protein, genetic material, and sometimes lipids. The genetic material in a virus can be RNA or DNA. The protein coat that surrounds the genetic material is called the capsid. Follow the directions. 1. Circle the genetic material in each virus. 2. Color the protein parts of each virus red. T4 Bacteriophage Tobacco Mosaic Virus Influenza Virus Head DNA Capsid Capsid 1. Where is the genetic material in a T4 bacteriophage located? 2. In general, is the genetic material in a virus inside or outside the protein parts? 3. Why do you think the word virus, based on the Latin word for poison, was used for these structures? BUILD Understanding` Venn Diagram A Venn diagram is made up of overlapping circles. It is a useful tool for comparing two or even three topics. As you read Lesson 1, complete the Venn diagram below with information about viruses and cells.

3 Viral Infections A bacteriophage is a virus that can infect bacteria. A lytic infection is one kind of viral infection. It results in lysis, or bursting of the host cell. A lysogenic infection is another kind of viral infection. It occurs when viral DNA inserts itself into the DNA of the host cell. The viral DNA is replicated along with the host cell DNA. Eventually, the viral DNA separates from the host DNA. It then directs the construction of new virus particles. The diagram below compares lytic and lysogenic infections. Use the sentences to complete the diagram. The proteins and nucleic acids assemble into new viruses. Viral genes are transcribed by the host cell. The virus injects DNA into a bacterium. The prophage may replicate with the bacterium for many generations. Prophage The viral DNA inserts itself into the bacterial chromosome, where it is called a prophage. LYTIC INFECTION LYSOGENIC INFECTION The prophage can exit the bacterial chromosome and enter a lytic cycle. Viral enzymes lyse the bacterium s cell wall. The new viruses escape and infect other bacterial cells. The bacterium makes new viral proteins and nucleic acids. 1. Which type of viral infection includes the formation of a prophage? 2. What happens after viral enzymes lyse the bacterium s cell wall?

4 Viral Infections Lytic Infections In a lytic infection, a virus enters a cell. It then copies itself and causes the cell to burst. Lysing is another word for this type of cellular destruction. The flowchart below summarizes what happens in a lytic infection. Follow the directions. 1. Use the following terms to complete the flowchart. bacterium viral proteins virus A enters or injects its DNA into a bacterium. The bacterium then makes and DNA. New viruses are assembled and burst out of the. 2. What is one result of a lytic infection? Circle the correct answer. destruction of the virus destruction of the host 3. What happens to the viruses after they lyse the cell wall? BUILD Connections How a Lytic Virus Is Like an Outlaw An analogy compares two things that are different and shows how they can be similar. 1. How does the analogy of the lytic virus to an outlaw help you understand lytic viruses?

5 20.2 Prokaryotes Lesson Objectives Explain how the two groups of prokaryotes differ. Describe how prokaryotes vary in structure and function. Explain the role of bacteria in the living world. BUILD Vocabulary A. The chart below shows key terms from the lesson with their definitions. Complete the chart by writing a strategy to help you remember the meaning of each term. One has been done for you. Term Definition Bacillus A type of asexual reproduction in which a prokaryote replicates its DNA and divides into two identical halves Coccus Conjugation A thick internal wall that encloses the DNA and part of the cytoplasm in a prokaryote A unicellular organism that lacks a nucleus A spiral- or corkscrew-shaped prokaryote

6 Classifying Prokaryotes A prokaryote is a unicellular organism that lacks a nucleus. Prokaryotes are classified into two groups. Most prokaryotes have a cell wall, a cell membrane, and cytoplasm. The bacterium below is one example of a prokaryote. Follow the directions. 1. Color the ribosomes yellow. 2. Color the cell membrane blue. 3. Color the flagellum red. 4. Color the pili orange. 5. Color the DNA green. 6. What does the bacterium use to move? Circle the correct answer. ribosome flagellum peptidoglycan 7. Circle the correct answer. Which structure is closest to the environment of the bacterial cell? outer membrane cell membrane cell wall 8. What is the function of the cell wall?

7 Structure and Function Size, Shape, and Movement Prokaryotes come in a variety of shapes. Shape is one way to tell different prokaryotes apart. The diagram at the right shows several kinds of bacteria. Follow the directions. 1. Color the bacilli blue. 2. Color the cocci red. 3. Color the spirilla yellow. 4. Describe the shape of bacilli. 5. Describe the shape of cocci. 6. Describe the shape of spirilla Diseases Caused by Bacteria and Viruses Lesson Objectives Explain how bacteria cause disease. Explain how viruses cause disease. Define emerging disease and explain why emerging diseases are a threat to human health. Bacterial Diseases For Questions 1-5, complete each statement by writing the correct word or words. 1. One way bacteria can cause disease is by breaking down and damaging of the infected organism. 2. Bacteria can also cause disease by releasing that harm the body. 3. A(n) is a disease-causing agent.

8 4. One way to control bacterial growth is by subjecting the bacteria to high temperatures during a process known as. 5. A(n) is a preparation of weakened or killed pathogens or inactivated toxins that can prompt the body to produce immunity to a disease. 6. What organs do the bacteria that cause tuberculosis typically damage? 7. What are antibiotics? 8. How are the causes of tuberculosis and diphtheria similar? How are they different? 9. Describe the similarities and differences of antibiotics and disinfectants. 10. Why should meat be cooked until it is well-done? Match the bacterial control method with an example of the method Bacterial Control Method Example 11. physical removal A. Putting milk in a refrigerator 12. disinfectant B. Using bleach to clean a countertop 13. safe food storage C. Using boiling water to clean dishes 14. safe food processing D. Washing hands 15. sterilization by heat E. Boiling soup Viral Diseases 16. What are some human diseases caused by viruses? 17. How do antiviral medications work? Why don t they also kill host cells? Write the letter of the correct answer on the line at the left. 18. A person has a low helper-t cell count. What viral disease does he or she most likely have? A. HPV C. hepatitis B B. AIDS D. chicken pox 19. A person has blister-like lesions on the skin. What viral disease does he or she most likely have? A. HPV C. hepatitis B B. AIDS D. chicken pox

9 Emerging Diseases For Questions 20-24, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true. 20. Pathogens are able to evolve over time. 21. A(n) noninfectious disease is an unknown disease that appears in a population for the first time. 22. The widespread use of vaccines has led to the emergence of resistant strains of bacteria. 23. Slight genetic changes would be needed for the bird flu virus to become infectious to humans. 24. Scrapie is most likely caused by pathogens known as viroids. Apply the Big idea 25. RNA viruses have shown an ability to evade antiviral drugs. How do you suppose this is possible, when viruses are not alive? How may the reproductive methods of viruses help the process? 26. Compare the processes of how a bacteria causes a disease verses how a virus causes a disease.