Name
Date
Class
Lab
18-1
EXPLORATION Viral Replication
V
iruses are very successful at invading the cells of organisms. A virus first becomes attached
securely to the outside of a host cell. Then, some viruses inject their nucleic acid into the
cell and leave their coat outside the cell; other viruses still have their coats when they enter the
cell. Once many types of viruses are inside a host cell, they insert viral genes into the host
DNA. The viral genes direct replication, causing the cell to make many new copies of viral
genes. At the same time, the cell’s protein synthesis machinery is directed to make many new
viral coats and enzymes. The virus particles are assembled, and the new viruses escape from the
cell either by exocytosis or by bursting out of the cell.
O BJECTIVES
• Trace the steps of viral replication in cells.
• Describe the steps of viral replication.
• Construct an analogy for viral replication in cells.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
MATERIALS
glue
scissors
photocopy of model viruses and viral parts
goggles
PROCEDURE
1. Study Figures 1 and 2 so that you become famil-
iar with viral structures and with the models of
viral structures that you will use in this
Exploration.
2. The teacher will give you a photocopy of draw-
ings that represent viruses and viral parts. Cut
out the drawings.
3. Each drawing corresponds to one of the num-
bered steps of viral replication listed at the end of
the Procedure. Using Figure 2 as a key, label the
tab on each drawing with the number of the step
of viral replication that it represents.
LABORATORY MANUAL
4. Examine Figure 3 under Data and Observations.
The diagram summarizes the steps of viral replication within a cell. The location of each step is
labeled. Match each cutout drawing with the correct label. Then copy the numbers from the
drawings onto the appropriate spaces provided in
the diagram.
5. Place each drawing over its corresponding label
in Figure 3. When complete, have your diagram
checked by the teacher for accuracy.
6. Once the drawings are in their proper positions
on the diagram, glue them in place.
CHAPTER 18 BIOLOGY: The Dynamics of Life
125
Name
Date
Class
Lab
18-1
Viral Replication
PROCEDURE
continued
Figure 1
Figure 2
Key for cutout drawings
Viral structure
1. The virus attaches to the host’s cell membrane.
2. The virus enters the cell.
3. The protein coat of the virus is removed.
4. Viral genes are activated.
5. a. The activated genes direct replication of viral genes.
b. The activated genes direct protein synthesis to make
new viral coats and enzymes.
6. a. New viral genes are completed.
b. New viral coats are completed.
7. The new viruses are assembled. Genes are inserted
into the protein coats.
8. The new viruses are released from the cell.
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CHAPTER 18 BIOLOGY: The Dynamics of Life
LABORATORY MANUAL
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Steps of Viral Replication
Name
Date
Class
Lab
18-1
Viral Replication
D ATA AND O BSERVATIONS
Life Cycle of a Virus
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Figure 3
LABORATORY MANUAL
CHAPTER 18 BIOLOGY: The Dynamics of Life
127
Name
Date
Class
Lab
18-1
Viral Replication
ANALYSIS
1. In what way is viral replication different from cell reproduction?
2. Examine your completed diagram of viral replication. What two processes are directed by
viral genes that are activated inside the host cell?
3. Describe the stage that occurs before viruses are released from the cell.
4. If you were a scientist developing a drug that would block viral replication, which steps
5. The analogy you are working with in this Exploration compares viral replication with the
making of a product in a factory. In what ways does the analogy not hold true?
FURTHER EXPLORATIONS
1. Read the article “Viruses Have Many Ways to Be Unwelcome Guests,” by Michael Balter, Science,
April 10, 1998, pp. 204–205. Write an essay that explains the different ways viruses invade host cells
and replicate.
2. Use the library to research retroviruses. Determine how their replication differs from that shown in
this Exploration. Change the factory analogy to account for these differences.
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CHAPTER 18 BIOLOGY: The Dynamics of Life
LABORATORY MANUAL
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
would you choose to block? Explain.
Teacher Guide
18-1 E XPLORATION
Viral Replication
Objectives
• Trace the steps of viral replication in cells.
• Describe each step of viral replication.
• Construct an analogy for viral replication in cells.
Process Skills
observe, recognize and use spatial relationships,
formulate models
Time Allotment
4. Answers will vary. One could block attachment
of the virus, block viral coat removal so cell
machinery is not taken over, block production
of either viral coats or viral genes so new viruses
could not be formed, or block the release of the
viruses.
5. Answers will vary. Viral replication involves the
use of a virus to make more viruses. When a
product is made in a factory, it isn’t made from
an existing product of the same kind. Also, factories usually aren’t destroyed making products.
Figure 3
1 class period
Materials
glue (15 bottles)
scissors (15)
photocopies of model viruses and viral parts (15)
goggles (30)
Preparation
• Make a photocopy of page T33 for each group.
Teaching the Lab
Have students work in pairs.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
• Emphasize the use of the key in Figure 2 before
beginning. Encourage students to go on to the
next step of viral replication if they can’t figure
out which cutout matches a particular number.
• Troubleshooting: If students are having problems, reinforce the idea that each cutout
matches a number in the steps of viral replication and that it also matches a label on the cell
diagram. The sequence of steps goes from top
to bottom on the cell diagram.
Data and Observations
See Figure 3.
Analysis
1. Cells reproduce on their own by mitosis or
binary fission. In contrast, viruses must infect
living cells and use the cells’ machinery in order
to replicate.
2. New viral genes and new viral coats are
produced.
3. The new viral genes are inserted into the new
viral coats.
LABORATORY MANUAL
ANSWER PAGES BIOLOGY: The Dynamics of Life
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