Inheriting Disease: Are You At-Risk?
Lesson 5 of 7
Objective: Students will be able to explore the relationship between genetic variation and environmental factors in the onset of heart disease. Students will also consider the implications of increased knowledge about genetic variation for disease prevention.
The goal of the lessons in this unit is to focus students’ attention on the practical, medical applications of understanding human genetic variation at a molecular level. The lesson Detecting Genetic Variation - Sickle Cell Trait looks at treatment options that become possible with the discovery and sequencing of a disease-related gene. In contrast this lesson focuses on the likelihood that genetic testing for common, multifactorial diseases will increase in the future and invites students to consider the prospects that this information will help individuals make wise decisions about their personal health. Specifically, students explore the rising trend of heart disease as an example of a common, multifactorial diseases that constitute the bulk of the healthcare burden in the United States and other developed countries.
Engage (Activate Student Thinking)
In this lesson, students will have an opportunity to explore the idea of medical risk and learn how genetic analysis is helping us understand and define people’s risks in new ways. Begin the lesson by asking students to suggest definitions of the term “risk.” You might prompt the discussion by asking students to think about risky behaviors that are a part of adolescence.
1. Chart or have a student in the class chart three or four of the definitions offered on an anchor chart or have each write their definition on a Post-it Note and post the note on a prepared anchor chart.
(Potential response: Students may suggest that “risk” refers to the chance that something bad or negative will happen, as, for example, the risk involved with dangerous behaviors. Help students see that one way to think about risk is in terms of one’s chance of experiencing a particular event; i.e teenage underage drinking and driving).
2. Ask students whether they think risks can be modified.
(For example, ask them if there is any way they can modify their risk of getting into a car accident, being robbed or their risk of a heart attack or of getting cancer.)
3. Read the following story aloud and ask students to hypothesize the cause of this unfortunate true event:
"The death of Olympic Champion Sergei Grinkov a young Russian figure skater, who along with partner Ekaterina Gordeeva had won two Olympic gold medals in the pairs competition and were expected to continue dazzling audiences and judges for years into the future, stunned the citizens of Russia. In November 1995, however, 28-year-old Sergei suddenly collapsed and died during a practice session. He was a nonsmoker, he was physically fit, and there had been no warning signs."
ASK: What happened to cause this young athlete’s early death?
4. After several volunteers have shared their hypotheses, explain that Sergei Grinkov was born with a mutation called PL(A2) in a single gene that affects the formation of blood clots. The mutation causes clots to form in the wrong places at the wrong time. If such a clot forms in one of the arteries that supply the heart, a heart attack can result.
a. Ask students to consider whether this mutant allele influenced Sergei Grinkov’s risk of a premature heart attack.
(The mutant allele increased Grinkov’s risk of premature heart attack relative to the risk for the general population. Relative risk is the risk for any given person (or group) when considered in relation to the rest of the population. One may have an elevated relative risk but still have a low absolute risk. For example, one may have an increased risk of 20 percent above the risk for the general population, but may still only have a 5 percent risk of suffering the disease in question by, say, age 50.)
b. Ask students to suggest ways that Sergei Grinkov could have modified his behavior had he known he was at increased risk for premature heart attack.
(Given that this single-gene disorder affects the clotting process, it likely would have been difficult to reduce the risk of heart attack by modifying the environment. There is some indication that the PL(A2) mutation can interact negatively with increased cholesterol concentrations in the blood, or levels. If, for example, plaques formed by excess cholesterol break off from the lining of a coronary artery and create a lesion in a blood vessel, the PL(A2) mutation can cause the formation of a clot that impedes blood flow, resulting in a heart attack. Maintaining low cholesterol levels through diet and exercise might thus reduce the risk of premature heart attack for a person who carries the PL(A2) mutation.)
Explore (Guided/Student-Centered Activity)
1. Distribute the "Rolling the Dice" Game, and direct students to work in groups of three to play the game described allowing approximately 10-15 minutes for each group to complete the game.
Ask how many students suffered a fatal heart attack.
2. Determine at which life stages the heart attacks occurred, and record this information on a class anchor chart as well as on the student data table provided.
Ask students how the game is and is not like real life.
(Potential responses: The game is like real life in that life expectancy depends on many risk factors. The game is not like real life because students rolled the die to determine what their risk factors would be instead of making personal choices. The game also involved only environmental risk factors, not genetic ones. If students fail to mention that the game does not address genetic risk factors, try to elicit that response by asking about Sergei Grinkov.)
Explain (Formulate Ideas)
Give each student in each group an envelope containing their relevant-genes and explain that this envelope contains information about his or her genetic risk for a fatal heart attack. Ask students to open the envelopes and share their heart points until you have addressed all four values: –10, 0, +10, +40. Point out that the genetic risk falls off rapidly as genetic relatedness decreases, from 40 points for first-degree relatives to no points for third-degree relatives. Explain that this is the case generally for multifactorial diseases.
Elaborate (Apply and Extend Understanding)
Give one copy of "Thinking About the Game" reflection sheet to each student, and ask students to compare the results of the game with and without considering genetic factors. As you conclude this portion of the lesson allow each group to offer its answer to one of the questions on the reflection sheet. Then, invite other groups to contribute additional insights or information to challenge ideas expressed by other groups.
There are many strategies for conducting productive group discussions with high school students however one of my favorites is the Socratic Seminar method. Dialogue regarding the influence of genetic factors lends itself perfectly to the use of this method. For additional consideration view the video "Socratic Seminar in Science" by the folks over at NWABR. Socratic Seminars can be helpful for fostering effective discussions in science classrooms, as seen in the two high school biotechnology classes featured in the video. It is truly inspirational to see students challenging each other and their instructor is the same fashion as many of the greatest thinkers in science must have debated their discoveries.
Evaluate (Monitor Understanding)
Student groups will create a sixty (60) second Public Service Announcement (PSA) explaining the connection between the genetic and environmental risks of heart disease using their mobile devices or classroom flip cameras. Students critique the PSA's of other student groups using the iVideo Critique Rubric and the PSA that earns the most "likes" or "stars" wins bragging rights!
Mrs. Cullen at Natick High School in Massachusettes has a great resource my students and I use for creating PSA's using Apple products; it is packed with great information to be used with any recording device!