56
i n ut e s
e ss
io
LE
-
1–2
50 -m
CT
40
to
ns
Joe’s Dilemma
ACTIVIT Y OVERVIEW
VI
EW AND
RE
F
SUMMARY
Students are introduced to the issue of genetic testing through a story about a student
who suspects he may have inherited a genetic syndrome (the Marfan syndrome). They
generate questions they would have if they were in this situation, and make a preliminary decision of what they would do based on the limited information they have
so far. Students then view a video produced by the National Marfan Foundation to find
out more. They consider the impact of the Marfan syndrome on a person’s life. Activity 67, “What Would You Do?” will follow up on this activity, enabling students to
make a recommendation to Joe after they have learned more about genetics.
KEY CONCEPTS AND PROCESS SKILLS
1.
Some medical conditions and diseases are genetic.
2.
Understanding the principles of genetics can help individuals make decisions
about genetic conditions and genetic testing.
3.
In some cases, the presence of a genetic condition can be established by
genetic testing.
4.
The Marfan syndrome is an inherited disease that affects a person’s connective
tissue and is characterized by a pattern of symptoms, some or all of which may
be displayed by an individual with the syndrome.
5.
A person with the Marfan syndrome can live a full productive life, but may
have to avoid some physical activities and monitor his/her health.
6.
Pediatric genetics and genetic counseling are careers that require a background
in genetics.
KEY VOCABULARY
gene
Teacher’s Guide
D-25
Activity 56 • Joe’s Dilemma
MATERIALS AND ADVANCE PREPARATION
For the teacher
1
Transparency 56.1, “Diseases”
*
blank transparencies or chart paper
*
overhead transparency pens or permanent-ink markers
*
overhead projector
video: “How Do Your Genes Fit?”
*
1
television monitor
*
1
videocassette recorder
*Not supplied in kit
Arrange to have the VCR and monitor set up. Preview the video.
TEACHING SUMMARY
Getting Started
1.
Introduce genetic diseases and the Marfan syndrome.
Doing the Activity
2.
Students read and respond to a fictitious e-mail by a student who has just
learned he may have the Marfan syndrome.
3.
Students view a video about the Marfan syndrome and respond to the
Analysis Questions.
Follow-Up
4.
Discuss what students have learned from the video and their reactions to the
information.
Extension
Students use the Internet to learn more about the Marfan syndrome.
BACKGROUND INFORMATION
The Marfan Syndrome
The Marfan syndrome was selected for this activity for three reasons: 1) it affects all
ethnic groups, 2) it can be difficult to be certain of a diagnosis in some cases, and 3)
an individual who knows he or she has the syndrome can take actions that significantly improve the individual’s health and extend average life span to nearly that of
the general population.
D-26
Science and Life Issues
Joe’s Dilemma • Activity 56
The Marfan syndrome is an inherited disorder of the connective tissue. Connective
tissue provides the glue and scaffolding of the body, and is present in all organs. It is
necessary for normal development and growth, cushions the joints, and holds tissues
and organs together. Because connective tissue plays so many roles, the Marfan syndrome has many symptoms. Some of the most common symptoms are related to the
following body systems:
•
Skeletal:
tall stature; long legs, arms, and digits, and sometimes a long face and jaw; loose
joints; abnormal spinal curvature; and a protruding or indented chest
•
Eye:
an abnormally positioned lens, nearsightedness, and (less common) retinal
detachment
•
Heart and blood vessels:
abnormal valves, and a widened aorta that can develop tears
The most life-threatening symptoms are those related to the heart and blood vessels.
Most individuals with the Marfan syndrome have some signs of abnormal structure
of the aorta detectable by an echocardiogram. Small tears between the inner and outer
surfaces of the walls of the aorta can enlarge and eventually rupture. Today, appropriate medical monitoring and care can prevent and treat the heart problems characteristic of the Marfan syndrome. Life expectancy has increased from an average of
approximately 45 years in 1972 to an average of approximately 70 years now. However, this increased life expectancy depends on diagnosis and appropriate actions,
including getting medical checkups for heart problems and avoiding contact sports
that can stress the heart. (More background information on the Marfan syndrome is
provided to both students and teacher in Activity 67, “What Would You Do?”)
Other Genetic Diseases
In this unit, we have avoided using more dramatically debilitating conditions such as
sickle cell anemia, cystic fibrosis, Tay-Sachs disease, and Huntington’s disease as examples of human genetic disorders for two reasons. First, they present a picture of genetics as relating only to very serious and emotionally difficult subjects that may be more
appropriate for older students. Second, with the exception of Huntington’s disease,
these conditions are quite specific to different ethnic groups. Therefore, we have not
made them central to the unit. Should students ask about them, some background
and references follow so you can respond.
Teacher’s Guide
D-27
Activity 56 • Joe’s Dilemma
Huntington’s disease, like the Marfan syndrome, is an example of a disease
caused by a single dominant gene. It is nearly always fatal, although initial
symptoms do not usually appear until after the affected person is 40. Each child
of a parent with these conditions has a 1/2 chance of inheriting the dominant
condition. Sickle cell anemia, cystic fibrosis, and Tay-Sachs disease are all recessive conditions. They can be carried in a family for many generations without
anyone being aware of them until a carrier has children with another carrier.
Each child of two parents with the recessive trait has a 1/4 chance of inheriting
the condition.
The table below summarizes the incidence of each of these conditions.
Disease
Main Group
Affected
Frequency
of carriers
in affected
population
Frequency
of affected
individuals
in affected
population
Consequence
Thick, sticky mucus secretions lead to coughing,
respiratory distress, and infections such as
3,200 live births pneumonia. Digestive problems also result.
Average life span has been lengthened to early
30s due to treatments.
Cystic fibrosis
Individuals
of Northern
European
descent
1/28 whites
Sickle cell
disease
Individuals
of African
descent
1/12 African- 1/400 AfricanAmericans
Americans
Sickled cells block blood flow in blood vessels,
leading to episodes of pain that may be mild
to severe. Infections sometimes result. Life span
and quality of life are improving due to treatment.
Tay-Sachs
Eastern
European
Jewish
1/30
Death typically results before age 5.
PKU (phenylketonuria) is another genetic condition that may be of interest, as
all newborns are tested for this defect shortly after birth. When the condition is
detected and treated soon after birth, individuals with PKU can lead healthy
and relatively normal lives, except for dietary restrictions until about age 10.
However, if a woman with PKU becomes pregnant, she must return to eating a
restricted diet in order to prevent undesirable effects on her unborn child as a
result of her condition. The special diet is low in certain types of proteins (those
with a high content of the amino acid phenylalanine), which are not metabolized normally in individuals with PKU. This leads to the build-up of metabolites that are harmful to normal development of the nervous system, particularly
during childhood.
D-28
Science and Life Issues
Joe’s Dilemma • Activity 56
Genetic Discrimination
At this time (late 2000), some states have laws against genetic discrimination for
employment and/or health insurance. However, the extent of the legal protection
varies. A few states have no laws against genetic discrimination at this time. Several
bills are under consideration at the federal level.
REFERENCES
Pyeritz, R. E. and C. Gasner. The Marfan Syndrome. New York: National Marfan
Foundation, 1994.
National Marfan Foundation. How Do Your Genes Fit? Port Washington, N.Y. 1996.
Teacher’s Guide
D-29
Joe’s Dilemma • Activity 56
TEACHING SUGGESTIONS
GETTING STARTED
1.
Use their responses to develop a chart or transparency of questions raised by the class. These questions will help you determine to what extent students are asking questions about the science that
Introduce genetic diseases and the Marfan
may help an individual in this situation, as well as
syndrome.
what assumptions they are making about genetic
Have students read the Introduction on page D-12
in the Student Book. If you taught Unit C, “MicroLife,” in Science and Life Issues, use 56.1, “Diseases,”
to review the different causes of disease; if not,
briefly highlight the fact that some diseases or
testing and inheritance in general. Some questions
will be related to how the syndrome is inherited, and
how accurate the tests are. Others will focus on the
symptoms and the chances of serious health problems or death as a result of the Marfan syndrome.
health conditions are not caused by infectious
Allow each group to suggest an advantage or disad-
agents. Some are inherited from an individual’s par-
vantage of being tested (in response to Step 3).
ents or grandparents. Encourage students to offer
Develop a similar transparency or chart to display
examples from their own experience.
these advantages and disadvantages. Advantages of
In this activity, students will be introduced to a
genetic condition and some of the issues faced by
an individual who may have inherited a condition
called the Marfan syndrome.
being tested generally fall into two categories: 1)
“knowing is better than worrying, and if I find out
I don’t have the syndrome, I can stop worrying,”
and 2) “if I know I have the syndrome, I can use the
information in a positive way and take precautions
Review the terms syndrome and connective tissue as
to ensure my health.” Disadvantages of being test-
introduced in the reading. Although these terms are
ed include: 1) some people may not be emotionally
not considered key vocabulary for the unit, they
prepared to deal with the information provided by
will help students understand the key ideas.
a positive test, and 2) the information might be used
in a negative way by others, such as by insurance
DOING THE ACTIVIT Y
2.
Students read and respond to a fictitious email by a student who has just learned he
may have the Marfan syndrome.
companies to deny health insurance. If students
argue, “I’d rather not know if I have the syndrome,
since there’s nothing I can do about it anyway,”
their response should be accepted. However, ask students how they can be sure there is nothing that can
Have students read the email from Joe to his friend
be done. The video to follow will refute this attitude
Megan. Then allow them to work in pairs or groups
with evidence. After the discussion, allow students
of four to discuss their responses to Steps 2 and 3.
time to add any new ideas to their tables.
They should record their answers and prepare to
present some of their answers to the class.
Teacher’s Guide
D-31
Activity 56 • Joe’s Dilemma
3.
Students view a video about the Marfan
the use of pedigrees and Punnett squares to predict
syndrome and respond to the Analysis
genetic outcomes. Have some students share their
Questions.
responses to Questions 4 and 5. Use the activity as
You may want to stop the video after every segment
so students have a chance to take notes on information they have gotten from the video. Do not try
to explain all the science behind the information
briefly presented in the video. Students will have a
chance to view the video again after they have
learned more about genes. Questions 1–3 and 5–6
can be answered individually. Question 4 can be
answered individually or discussed in groups or
with the class.
n Teacher’s Note: It is possible that, as a result of
an opportunity to encourage a respectful discussion
of individuals with the Marfan syndrome or other
conditions. Stress that students should not in any
way demean or make fun of individuals who may be
perceived as different. You may wish to score student responses to Question 3 using the U NDER STANDING
Extension
Students use the Internet to learn more about the
Marfan syndrome.
Students can go to the SALI page of the
this activity, a student in your class may become
SEPUP website for links to web-
concerned that he/she has the Marfan syndrome.
sites on the Marfan syndrome
Emphasize that individuals with the Marfan syn-
and other genetic conditions.
drome usually exhibit several of the signs discussed
in the video, and that anyone concerned should
SUGGESTED ANSWERS
check with his or her pediatrician. As more is
TO ANALYSIS QUESTIONS
known about the syndrome, most people are diagnosed in childhood. The health benefits of knowing
one has the syndrome are clear. Individuals with the
Marfan syndrome can now expect long and healthy
lives as a result of advances in treatment and prevention of negative effects.
C ONCEPTS (UC) variable.
1.
What are the signs that suggest a person may have
the Marfan syndrome?
The typical signs are a long, narrow face; tall,
slender stature; long arms, legs, fingers, and
toes relative to overall height; double-jointedness or loose joints; nearsightedness; and cur-
FOLLOW–UP
4.
vature of the spine.
Discuss what students have learned from
A person with the Marfan syndrome may not
the video and their reactions to the
have all these signs, but having most of them
information.
does suggest a person should consider consult-
Hold a brief discussion to summarize the informa-
ing with a doctor. Usually a person with the
tion provided in the video. Students will have a
Marfan syndrome notices health problems by
chance to watch the video again after they learn
the time he or she reaches adulthood, but some-
more about dominant vs. recessive traits and about
times doesn’t know the cause.
D-32
Science and Life Issues
Joe’s Dilemma • Activity 56
2.
There also may be anxiety about looking differ-
What causes the Marfan syndrome?
ent, if the person is very tall or wears thick glass-
The Marfan syndrome is caused by one altered
es. However, individuals with the Marfan syn-
gene. (The affected person usually inherits this
drome can participate in most activities and are
gene from an affected parent, but in about 1/4
successful in a wide array of jobs. Students may
of all cases the gene seems to be the result of a
note that having the Marfan syndrome will
spontaneous (new, random) mutation in the
have less of an effect on a person’s life if others
developing egg or sperm. In these cases, the
are sensitive to the individual and do not tease
individual’s parent does not have the gene, but
the person or treat the person as different. Stu-
the individual does, and can pass the gene to
dent answers will vary. Encourage a sensitive
his/her offspring.)
discussion of this question and a thoughtful
3.
Can you “catch” the Marfan syndrome from UC
another person, the way you can catch the
flu? Explain.
discussion of diversity.
5.
Look back at the questions you wrote in your
science notebook for Step 2 of the Procedure.
A complete and correct level 3 response follows:
a.
No, you cannot catch the Marfan syndrome
the new information you learned from the video.
from another person. You can catch only infectious diseases, which are caused by microbes
b.
(viruses, bacteria, and small organisms). The
Students should find that at least some of their
passed on in a gene from a parent to his or her
questions about the symptoms and seriousness
child. (A level 4 response might add the follow-
of the Marfan syndrome were answered. They
ing: The only other way to get the gene is
may have additional questions about the pedi-
through a mutation. Then the gene can be
gree briefly shown in the film. They will learn
passed on to the person’s offspring.)
What effect can the Marfan syndrome have on a
person’s life?
Some of the following ideas may come up after
discussing the video or later in the unit as students learn more. Having the Marfan syndrome
usually means that a person must avoid certain
kinds of physical activity, such as contact
sports, and avoid overexertion. The person
probably will have more doctor’s appointments
What new questions would you want to ask a
doctor or genetic counselor?
Marfan syndrome is an inherited disease that is
4.
Were any of your questions answered? Record
more about this later in the unit.
6.
Reflection: How would you behave toward a fellow student whom everyone suspects has the Marfan syndrome?
Students should describe treating the person
with respect. They may also mention involving
the student in activities that do not overexert
him or her and discouraging the affected student from playing in contact sports that can
stress the heart.
than usual, especially to monitor the eyes and
heart, and may be anxious about health issues.
Teacher’s Guide
D-33
Science and Life Issues Transparency 56.1
germs
and are caused by
infectious
©2001 The Regents of the University of California
genes
environment
are
Diseases
lifestyle
and are caused by
combination
of factors
noninfectious
Disease
D-35