Pick the Risk: "Does It Run in Your Family?"
Lesson 13 of 19
Objective: SWBAT use a pedigree chart to learn about how chronic diseases run in families caused by multiple genes.
To engage students in lesson I conduct a class survey where I ask students to raise their hand if they have family members who have or have had diabetes or heart disease.
I follow this up by asking students the following question:
Do you believe that common diseases like heart disease, diabetes, or colon cancer have a genetic component? (Meaning do you believe it's in your DNA?)
I end this section of lesson by asking students if they have any ideas why they believe Hispanics are 2 times more likely to have diabetes? Possible answers can be environment such as food and attitudes towards exercise, as well as genetics.
This approach of using diabetes as the lesson entry point applies to all students. Current statistics compiled by the American Diabetes Association are disturbing. June 2014 data shows 9.3% of the U.S population has diabetes. That's almost 1 out of every 10 people. It gets scarier. In 2012, 86 million Americans age 20 and older had prediabetes; this is up from 79 million in 2010.
Many people do not realize how serious diabetes is. The tendency is to think of it as inconvenient - you have to take insulin shots and watch what you eat. The truth is far more sobering. Diabetes causes blindness, strokes, amputations, heart disease and much more.
In this section of lesson students complete Pick the Risk courtesy of the Genetic Science Learning Center.
In this activity students are challenged to track and record the passage of colored pom poms (representing genes) through generations of a family using a pedigree. Students learn that common chronic diseases (such as diabetes) run in families and are caused by the combined action of multiple genes. (SP2 - Developing and Using Models)
- Most common diseases are caused by the combined action of multiple genes and environmental factors. (CCC - Cause and Effect)
- Many common diseases (such as diabetes) run in families and have a genetic component.
- An individual's risk of developing a common disease is estimated by looking at siblings, parents and grandparents in a family medical history.
Copies of student pages (Pick the Risk)
Colored pom poms
Prior Knowledge Needed
- Genes are inherited from parents to offspring and contribute to observable physical traits. (MS-LS3-2- Sexual reproduction results in offspring with genetic variation)
- Pedigrees are used to track genetic information
Students may think that all heritable traits (and genetic disorders) are caused by a single gene and exhibit dominant or recessive patterns of inheritance. But more commonly, traits result from the combined action of many genes and environmental factors. Such multifactorial traits can exhibit varied and complex patterns of inheritance that are not easy to predict.
Point out that this activity differs from reality in the following ways:
» The number of genes contributing to a polygenic disease is usually not known.
» The number of genes carried by parents or offspring that can increase heart disease risk is not known.
» Environmental factors can also vary an individual’s risk of developing multifactorial diseases.
Emphasize that these are a few of the reasons why diabetes and other common diseases are so complex, and why the inheritance patterns for such diseases are difficult to predict.
Therefore, individuals are placed in general categories (high, medium, or low risk groups) based on features from their family health history that correlate with a certain probability of developing a disease.
» For example, it is said that an individual who has a parent (or possibly a grandparent) with heart disease may be “at risk” and should take steps to protect themselves.
Siblings, parents, and possibly grandparents, are informative when assessing an individual’s risk of developing a common disease and need be included in a family health history. It is unlikely that all of the same risk factors (genes) will be present in less closely related family members.
Discuss why each feature in the chart indicates an individual may be at increased risk for developing heart disease.
» Each feature indicates that the family has accumulated more risk factors (genetic or environmental). Therefore, an individual in this family is more likely to develop disease.
Discuss behaviors and choices that can reduce an individual’s risk of developing heart disease.
Conclude the class discussion by reminding students that genetic susceptibility does not mean an individual will inevitably inherit a disease. Positive lifestyle changes and healthy living can reduce genetic risk dramatically. That is why it is so important to know your family health history. If you know you are “at risk” you can take steps to protect yourself.
In addition I visit the American Diabetes Association which has a great Genetics of Diabetes page that compares and contrast the genetic component of both Type 1 and Type 2 diabetes.
In this section of lesson I show students the Genetics and Diabetes video that discusses how genetics is one contributing factor in the development of diabetes. Most critically, it emphasizes that environment (i.e. nutrition and physical activity) plays a large role on the potential impact diabetes may have on your health.
Students are required to write down 5 important facts as they watch the video, I specifically emphasize information about how one can lower the risk of developing diabetes by exercising and eating properly.
I like to point out to my students that having a genetic predisposition doesn't guarantee that you're going to develop diabetes. BUT it should guarantee that you take extra care of yourself since you're at an elevated risk to develop disease.
In this section of lesson I revisit the opening question of the lesson: