YOU GAVE ME WHAT?
In this lesson and its extension the students will have an opportunity
to learn how an infectious disease such as AIDS may be quickly transmitted
throughout a population. Video has been chosen to help students understand
the basic structure and function of viruses. Some background as to the structure
of cells and how the DNA and RNA molecules function is necessary to the
understanding of this activity. Students will develop an understanding of
how viruses and retroviruses differ in their use of DNA and RNA. The students
will conduct a simulated transmission of an infectious disease and mathematically
determine the number of possible infected individuals based on the data
Our Human Body #10: Viruses
Teens Talk Aids #1: Teens Talk Aids
Students will be able to:
- describe the structure of viruses and explain how they reproduce;
- explain the role of antibodies in fighting viruses;
- mathematically determine the size of viruses using the unit micrometers;
- construct a model of disease transmission using acids and bases;
- explain the difference between AIDS and other viruses, including retroviruses.
Transmission of Diseases:
one of each of the following per student:
- small stock bottle of solution (either neutral or base)
- small test tube
- small test tube holder
- phenolphthalein indicator solution (one bottle for entire class)
Have the students brainstorm and come up with as many diseases
as they can that are caused by viruses. Ask the students to compare the
size of viruses to bacteria or other cells with which they may be familiar.
Go over the unit micrometer with the students and be sure they understand
this unit of measurement.
The focus for viewing is a specific responsibility or task(s)
that the students are responsible for doing while viewing the video, or
after seeing video, to focus and engage students' viewing attention. In
this first segment of the video I would like to divide the class into three
sections. The first section will be responsible for answering the question
"What is a virus"? The second group will answer the question "How
do we know what viruses look like'? and the third section will answer the
question, "How big is a large virus"?
BEGIN the video Our Human Body #10 Viruses with the title
showing on the screen. PAUSE when SciFax along with the question
"How big is a large virus" appears on the screen. Have the students
respond to the questions they were responsible for in the focus for viewing
section. Note to the Teacher: the video may not have provided sufficient
information to answer all the questions at this point. Therefore, the focus
for viewing should continue.) Also at this time go over the unit micrometer(micron).
Make sure each student understands this unit. The question in the video
indicates that 75,000 large viruses would be one inch in height. Have the
students convert this to micrometers and therefore have a better understanding
of the unit and the small size of viruses. RESUME the video and PAUSE
when the two word heading viral infection appears on the screen. Answer
the remaining questions from the first section. Also the students should
be able to respond to the following questions at this point. How do viruses
reproduce? Why do some scientists feel that viruses should not be considered
living? What is a host? Why are all viruses parasites? RESUME the
video and STOP when the SciFax question appears on the screen. "More
than 350,000 AIDS cases were reported between 1981 and 1991." How many
recovered? Also check the students knowledge of the following questions.
What is an antibody? Why is medicine often ineffective against viral infections?
What is the role that viruses may play in genetic engineering? Why is it
not important that a virus kill the cell?
FOCUS FOR VIEWING
This focus for viewing is for a different video Teens Talk AIDS. The video
is approximately 30 minutes in length, but I have chosen to use only about
4 minutes of the tape. This video is to develop the mind set that an infectious
disease can happen to anyone, Also this segment will help prepare the students
for the post viewing activities. To give the students a specific responsibility
while viewing divide the class into two groups. Have the first group be
able to list three specific questions the person at the testing center asked
the test subject when he came in to get tested for HIV. Have the second
group of students be able to list two precautions the tester gave to the
test subject after he told him he had tested negative for the HIV virus.
Note to the Teacher: Some of the responses that group number one should
provide are: How many different sex partners have you had? Have you been
using condoms? Have you had sex with a male? Have you had sex with a prostitute?
Responses from the second group should include: Take as many precautions
as you can, such as wearing condoms, or do not share needles. Abstinence
was not mentioned. This would be a teacher preference as to whether you
want to discuss this aspect.
BEGIN the video Teens Talk Aids #1 when the girl in the pink top
responds "I don't have that attitude that it can't happen to me."
This is approximately 8 minutes into the video. PAUSE when the young
man is shaking hands after being tested for AIDS. Have the students react
to this portion of the video. FAST FORWARD to the portion where the
young man is making a return visit to the testing center. RESUME
play at this point and STOP when he is ready to leave the testing
center. Again have the students respond to his actions when he found out
he did not test HIV positive.
At this point the students should have a good concept of what
a virus is and how it is transmitted. Review with the students what is meant
by the terms communicable and transmission. You may also wish to review
the terms base and indicator at this time, if your students are not familiar
with those terms. This activity is designed to show students how they could
give or get a communicable disease from someone. You may choose to use any
communicable disease you wish.
Note to the teacher: a good base solution to use is a weak sodium hydroxide
solution. Mix 4 grams of sodium hydroxide pellets with 1000 mL of water.
A weak solution of other bases such as household ammonia will also work.
Try to choose something which is odorless, when in a dilute solution. You
need as many stock solutions as you have students in the classroom. Number
each of the containers to keep track of the "infected" one. To
prepare a 1% phenolphthalein solution, dissolve 1 g of phenolphthalein in
99 mL of distilled water.( If phenolphthalein is not available, some laxative
pills contain this substance and a solution can be made from them). Each
student needs their own dropper. Water works well for the neutral pH solution.
However, I would suggest testing the water first. Some parts of the country
have many minerals in the water, so do not assume it is neutral. Have all
students use the same dropper for the indicator, so the indicator itself
will not be "infected". The activity has minimal safety risks
involved. However, if safety glasses and laboratory aprons are available,
it would be recommended they be used. If students spill any of the liquid
on their skin, have them rinse it off with water, immediately. After completion
of the activity, rinse the tubes and droppers with a weak acid, such as
vinegar. A base residue will cause the tubes to turn pink the next time
you use them, before you want them to!
1. On your data table is a place for you to write your hypothesis, do so
at this time, before obtaining your solution.
2. Obtain a numbered bottle of solution. Record the bottle number on you
data sheet. Most solutions are neutral, and students having such solutions
will represent healthy persons in the model. Someone in the class will be
given a bottle containing a dilute base. This person will represent the
3. Use your dropper to transfer two droppersful of your solution into your
4. When your teacher gives you the signal, begin the first round of transfers.
Choose a classmate at random. Fill your dropper from your test tube, and
have your chosen classmate do the same. Then each of you transfer the dropperful
into the other one's test tube. Record the name of the student on your data
sheet. Trade with only one student per trial.
5. When you teacher gives the signal, carry out a second round of transfers,
choosing a different classmate.
6. Record the name of the second round classmate on your data sheet.
7. For the third round choose still another classmate.
8. Your teacher will now place two drops of phenolphthalein indicator into
your test tube. Record the color of the solution. Note: the neutral solution
will remain colorless, but the basic solution will turn pink.
9. On your data sheet list the names of all the students who are "infected"
(who have pink solutions).
10. Obtain from the "infected" students the names of all their
contacts, by round, and record their names.
11. To deduce the identity of the first "infected" students, cross
off the names of the uninfected students from the data table. This should
allow you to narrow down the infected students from the first round to two
students. Those two students should obtain a sample from the stock solution
with the same number, and test it with phenolphthalein.
12. Use this information to infer who must have transmitted the disease
13. On your data table design a chart with student names and arrows to show
the transition route from one round to the next.
Have a health professional speak to the class about infectious
Have a research scientist speak to the class, on the difficulties of using
medicine to treat viral infections.
Science: Have students research the number of people
"infected" with AIDS each of the past ten years, and prepare a
graph. Also determine per unit of time, such as per minute, how many people
Art: Have students make a three-dimensional model of a virus. Social
Studies and Geography: Have students color code various regions of the world
and representative numbers of AIDS infection.
Science: Research why viruses may be helpful in genetic engineering.
Math: The unit to measure the size of a virus in usually micrometers.
Do some calculations to show students understand the relationship between
meters, centimeters, millimeters and micrometers.
Speech and Debate: Discuss: If you were the leader of your country,
where would you rank finding a cure for AIDS among all other national concerns?
Health: Discuss the prevention of sexually transmitted diseases(STD).
Science: Use the video Discovering Great Minds of Science "Viruses"
by Robert C. Gallo. Pangea Digital Pictures, 2246 Camino Ramon, San Ramon,
Science: Use Laser Disk Series, "The Living Textbook" by
Addison-Wesley Publishing Company.
Master Teachers: Dennis Reule and Cindy Yocum
Click here to view the
worksheet associated with this lesson.
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