To explore the genetic contributions to human disease.
This lesson uses a resource at a website created for the traveling science exhibit, RACE: Are We So Different?, developed by the American Anthropological Association in collaboration with the Science Museum of Minnesota. In this lesson, students learn that the impact of disease is influenced by genetic factors. They also learn that no disease is confined to any particular set of people grouped by "race," which is a problematic social term linked to skin color, not a biological term.
For students at the high-school level, learning is best accomplished by drawing on prior knowledge as a bridge to engagement with new and more complex concepts. In terms of the study of biology, students at the high-school level have begun to incorporate abstract concepts of biology about DNA, genetic transmission, and expression of traits, which they can now apply to the study of disease. (National Science Education Standards, p. 181.) High-school students have a basic understanding of the digestive, circulatory, musculoskeletal, and respiratory systems. They can use this knowledge to build their understanding of diseases that affect these systems and to learn about the immune system. High-school students may need support to grasp specific mechanisms and processes related to health and disease. (National Science Education Standards, p. 193.)
The expectation for high-school students is that they should be able to draw on their understanding of normal health function to new learning about dysfunction that occurs through hereditary and environmental stimuli. They can be encouraged to explain disease in physiological, molecular, or systems terms. (Benchmarks for Scientific Literacy, p. 146.)
High-school students are ready to understand that the “severity of disease symptoms is dependent on many factors, such as human resistance and the virulence of the disease-producing organism. Many diseases can be prevented, controlled, or cured. Some diseases, such as cancer, result from specific body dysfunctions and cannot be transmitted.” (National Science Education Standards, p. 197.)
Familiarize yourself with the RACE: Are We So Different? website, a section of which is the resource used for the development of this lesson. Also review the Teacher Resource, Understanding Human Genetic Variation, from the National Institutes of Health. This resource can help you lead the discussion in the Motivation activity.
Open the lesson by reading or paraphrasing this paragraph from the Teacher Resource, Understanding Human Genetic Variation, produced by the National Institutes of Health:
One of the benefits of understanding human genetic variation is its practical value for understanding and promoting health and for understanding and combating disease. We probably cannot overestimate the importance of this benefit. First, virtually every human disease has a genetic component. In some diseases, such as Huntington disease, Tay-Sachs disease, and cystic fibrosis, this component is very large. In other diseases, such as cancer, diabetes, and heart disease, the genetic component is more modest. In fact, we do not typically think of these diseases as “genetic diseases,” because we inherit not the certainty of developing a disease, but only a predisposition to developing it. In still other diseases, the genetic component is very small. The crucial point, however, is that it is there. Even infectious diseases, diseases that we have traditionally placed in a completely different category from genetic disorders, have a real, albeit small, genetic component.
Now students should use their Who Gets Sick? student esheet to watch the seven-minute video, Science Bulletins: Genes and Health—Moving Beyond Race (you can see this video on the esheet as well). This video describes how researchers at the University of California—San Francisco are working to identify the specific genes that contribute to asthma. They are doing so by going beyond current concepts of race to consider the human genetic variation that has evolved as the human species spread across the globe over the past 150,000 years.
Prompt discussion by sharing four statements made in the video. Ask students to amplify on the statements or to share any questions that the statements raise for them. Students can record their thoughts on the Who Gets Sick? student sheet.
- “When we use words like ‘black,’ ‘white,’ or ‘race,’ we are not being scientific. We are not being clear. We are looking at the color of their skin instead of their biology.” (0:05, Charles N. Rotimi, Ph.D., the director of the Center for Research on Genetics and Global Health)
- “Human genetic variation is the result of groups that have lived isolated from each other for a very long time.” (2:26, Dr. Rotimi)
- “We use ancestry right now because it gives us a clue as to where to find the gene that’s involved in the pathogenesis of asthma … When we know those specific genes, we can genetically test each individual and determine what their risk factor is at a given region of the genome, and forget about those notions of race and ethnicity.” (5:25, Esteban Gonzáles Bouchard, M.D., Physician Scientist, Center for Genes, Environments & Health, University of California–San Francisco)
- “Asian, European, African, Hispanic—those are all short-hands that will go away with time. When we actually know what genes individuals carry, then we can look at the whole genome in a systematic manner and see if we will find things that may be related to disease or health. And once we are able to do that, then race is completely irrelevant.” (5:59, Dr. Rotimi)
Do not correct student ideas in the discussion, and encourage questions. In the course of the lesson, they will have the opportunity to clarify their understanding of human genetic variation and the distribution of genetic diseases. After the class discussion, have each student write in their science journals a response to one or more of the above statements.
Begin by having students use the student esheet to visit Health Connections, which is a resource at the website, Race: Are We So Different? This resource provides an introduction to three complex diseases: sickle cell disease, hypertension, and age-related macular degeneration (AMD). After students have explored this resource, lead a brief discussion about them. Discussion prompts are presented below, along with facts drawn or inferred from the resource.
- Describe the effects of each disease:
- Sickle-cell disease—Causes severe pain and anemia
- Hypertension—Can lead to kidney damage
- Age-Related Macular Degeneration—Can lead to vision loss
2. Describe how genes may contribute to the development of each disease:
- Sickle-cell disease—Genes affect the shape of red blood cells. Sickle-shaped blood cells may provide protection from malaria; too many of these misshapen cells may clog the blood stream and lead to organ damage.
- Hypertension—Genes regulate the body’s response to stress; the disease is correlated with mental stress and increased cardiovascular response.
- Age-Related Macular Degeneration—Genes regulate the body’s immune system; the disease is correlated with an immune system response to certain types of infection early in life.
3. Provide an example of how development of the disease can be ameliorated through environmental interventions:
- Sickle-cell disease—Symptoms can be curbed through use of medication.
- Hypertension—Disease effects can be avoided or reduced through proper diet and avoidance of stress.
- Age-Related Macular Degeneration—Disease effects can be avoided or reduced through diet and avoidance of smoking and long-term exposure to the sun.
4. Explain any links between these diseases and a person’s skin color.
- Sickle-cell disease—There is no link between the disease and a particular skin color. There is a link between the disease and ancestry that can be traced back to geographical areas affected by malaria.
- Hypertension—There is no link between the disease and a particular skin color. There is a link between the disease and long-term stress.
- Age-Related Macular Degeneration—There is no link between the disease and a particular skin color. There is a link between the disease and longevity, and between the disease and exposure to certain infections early in life.
As followup, direct students to take the ten-question Human Variation Quiz.
- Learning About Sickle Cell Disease (National Human Genome Research Institute)
- Sickle Cell Disease (National Library of Medicine)
- Sickle Cell Disease (Genetic Science Learning Center, Universty of Utah)
- Sickle Cell Disease
- Disease & Mutation: Sickle Cell (3-D Animation Library, DNA Learning Center, Cold Spring Harbor Laboratory)
Students should follow the instructions on the student sheet.
In the lesson's video, Dr. Rotimi states, "Human genetic variation is the result of groups that have lived isolated from each other for a very long time.” National Geographic’s Genographic Project may help students better understand this statement. The Project is using advanced DNA analysis to explore the question of where in Africa humans originated and the patterns by which they spread across the world. It is collecting DNA samples from the general public to help unfold the migration paths of humanity’s ancient ancestors. Participating individuals can learn the details of their “deep ancestry.”
Genetics intertwine with environment to affect expression of mental as well as physical disorders. This topic is covered in How Do Mental Disorders Emerge from the Mix of Genes and Environments? It is a chapter from a book published by AAAS entitled, Behavioral Genetics: An Introduction to How Genes and Environments Interact through Development to Shape Differences in Mood, Personality, and Intelligence.