Name: ______Date: ______
Student Exploration: Virus Lytic Cycle
Vocabulary: bacteriophage, capsid, host cell, lyse, lytic cycle, virus
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. A computer virus is a program that can copy itself and infect a computer without the permission of the owner. How do you think a computer virus compares to a real virus?
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2. Have you ever been infected with a virus, such as the cold virus or flu virus? ______
3. If so, how did the virus affect you? ______
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Gizmo Warm-up
A virus is a microscopic particle that can infect a cell. Viruses are primarily composed of a protein coat, called a capsid, and nucleic acid. In the Virus Lytic Cycle Gizmo™, you will learn how a virus infects a cell and uses the cell to produce more viruses.
1. Viruses are extremely small. A typical virus is about 100 times smaller than a single cell, such as a bacterium. Label the virus and a bacterial cell in the image at right.
2. Bacteriophages are viruses that infect bacteria. Based on the diagram at left, label the head, tail, tail fibers, and the strand of nucleic acid in the image at right.
Activity A:Lytic cycle / Get the Gizmo ready:
· If necessary, click Reset (). /
Introduction: Unlike living organisms, viruses cannot reproduce on their own. Instead, viruses infect host cells, taking over the cell’s machinery to produce more viruses. This process is called the lytic cycle.
Question: What are the steps of the lytic cycle?
1. Observe: Use the navigation arrows on the DESCRIPTION tab to read about the stages of the lytic cycle. Using your own words, summarize each step of the cycle.
Step / Summary1 /
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2 /
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3 /
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4 /
↓
5 /
(Activity A continued on next page)
Activity B:Spread of infection / Get the Gizmo ready:
· If necessary, click Reset. /
Question: How does a viral infection spread?
1. Predict: Suppose that a virus infects a small population of bacteria. Predict how the numbers of viruses, infected cells, and uninfected cells will change as the infection progresses. On the blanks below, write increase, decrease, or stay the same.
Viruses: ______Infected cells: ______
Uninfected cells: ______
2. Observe: Click Play (), and watch the simulation. Describe what you see.
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3. Test: Click Reset, and Select the BAR CHART tab. Turn on Show numerical values. Click Play, and watch each bar as the simulation runs. What do you notice, and how does this compare to your predictions?
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Student Exploration: Disease Spread
Vocabulary: disease, epidemic, infect, infectious disease, pathogen
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
4. Why do you think it is important to cover your mouth when you cough? ______
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5. Why should you always wash your hands before you eat? ______
Gizmo Warm-up
When a person has a disease, his or her normal body functions are disrupted. Some diseases, such as diabetes and most cancers, are not spread from one person to another. But other diseases, such as the flu and strep throat, can be spread. These diseases are known as infectious diseases. Infectious diseases are caused by viruses, bacteria, and other agents known as pathogens.
In the Disease Spread Gizmo™, you will be able to observe how various pathogens can spread through a group of people. Click Play () and observe.
3. Describe what happened on the SIMULATION pane: ______
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4. Look at the color key on the bottom right of the Gizmo. What is happening when a person changes color? ______
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Activity A:Person-to-person transmission / Get the Gizmo ready:
· Click Reset ().
· On the CONTROLS tab under Active Diseases, turn off Foodborne and turn on Person to person.
· Set the Number of people to 5. /
Question: What factors affect how quickly a pathogen spreads from person to person?
2. Identify: Select the SIMULATION tab on the left and the TABLE tab on the right. (You will want the table tab open to answer question C.)
A. What does the purple person represent? ______
B. Click Play, and observe the simulation for a while. What must happen for the disease to spread from one person to another? ______
C. How long did it take to infect five people? ______
3. Experiment: Click Reset. Change the Number of people to 15. Click Play, and record how long it takes to infect five people. Then repeat the experiment when there are 25 people and 35 people in the room.
Number of people in room / Time required to infect five people (hr)15
25
35
4. Interpret: Study the data you collected. What trend do you see in the data, and how would you explain it? ______
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Activity B:Foodborne and airborne transmission / Get the Gizmo ready:
· Click Reset.
· On the CONTROLS tab under Active diseases, turn off Person to person and turn on Foodborne. /
Question: How do foodborne and airborne pathogens spread?
1. Observe: Select the SIMULATION tab. Click Play and closely watch the people moving around the room.
A. What does each person do just before becoming infected? ______
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B. How are foodborne pathogens transmitted? ______
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C. If a person in the simulation never eats or drinks anything from the buffet table, is it possible for them to become sick with the foodborne disease? Explain your answer.
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Activity C:Observations / Get the Gizmo ready:
· Click Reset ().
· Make changes to the simulation. Describe what happens. /
1. Change #1:
a. Describe what you changed:
b. What was the result?
2. Change #2:
a. Describe what you changed:
b. What was the result?
3. Change #3:
a. Describe what you changed:
b. What was the result?