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        Risky Genetics

        In this lesson from NOVA scienceNOW, students explore genetic testing for specific diseases, and consider the pros and cons of discovering a person's genotype for a particular disease.

        Lesson Summary


        In this activity, students play the role of doctors interpreting patients' genetic test results. They create characters, analyze genetic test results for three diseases, compare their characters' risks of developing specific diseases, and assess the risks for the next generation.


        Students will be able to:

        • Define the terms genotype, homozygous, heterozygous, recessive, and dominant
        • Apply the above terms to diseases with different inheritance patterns
        • Differentiate between genetic risk and lifestyle risk, in the context of disease
        • Demonstrate the use of Punnett squares to predict the probabilities of particular genotypes in a future generation
        • Construct a three-generation pedigree
        • Discuss how disease can be affected by lifestyle
        • Debate the pros and cons of genetic testing

        Grade Level: 9–12

        Suggested Time

        • One class period

        Media Resources


        Before the Lesson

        • Make copies of the Student Handout (one per student)
        • Copy the Teacher Blackline master, which contains eight pedigrees. Make enough copies of the sheet so that there is a pedigree for each student (e.g., three copies for a class of 24). Cut the pedigree strips apart and put them in a box or bag.
        • Provide computer access for each group of students
        • Ask students to bring in dice from home; have extras on hand for those who forget
        • Read the Teacher Notes—Risky Genetics PDF Document for background information and assessment tools
        • Bookmark the Web sites for the media resources

        The Lesson

        1. As a class, watch NOVA scienceNOW: Public Genomes Video (13:22)

        2. Ask students what questions they have about the video, and explain that they will now explore genetic testing for specific diseases: breast cancer, lung disease, and Alzheimer's. Students will play the role of genetic counselors who counsel patients about their genetic test results for genes associated with these three diseases. Students will pair with a partner, and by rolling dice and following steps provided in the handout, each "counselor" will create a male or female character with a unique genotype. Then students will analyze genetic data for their "patients," compare their characters' risks of developing the diseases, and predict the disease risks for the next generation.

        3. If necessary, review relevant terms and concepts, including:

        1. Allele: one of the variant forms of a gene
        2. Gene: a functional portion of DNA that is passed from parent to offspring and which usually codes for a specific protein
        3. Dominant allele: an allele that almost always results in a specific trait, even if the person possesses only one copy
        4. Recessive allele: an allele that only results in a specific trait if the person possesses two copies of the recessive allele
        5. Genotype: the genetic identity of an individual
        6. Heterozygous: having two different forms of a particular gene
        7. Homozygous: having two of the same forms of a particular gene
        8. Punnett square: a tool used to predict the genetic outcome of a mating
        9. Pedigrees: a pictorial representation of a family's health history
        10. Demonstrate a sample Punnett square on the board, such as the following, which shows a heterozygous parent (Bb) mating with a homozygous recessive (bb) parent:

        4. Give each student a copy of the handout, and break the class up into pairs. Make sure each pair has at least one die. (Before students do steps 5 and 6, make sure they know how to construct pedigrees. When they are ready to begin step 5, have them select a pedigree strip.)

        5. Instruct students to follow the procedure on the student handout, including watching the videos and reading the text on the following sites:

        6. When students are finished, lead a discussion. Ask the "counselors" to report their patients' results and recommendations. Note that students who drew the same pedigree will likely have made different recommendations. Ask:

        1. Did the recommendations differ among the patients?
        2. In terms of the subsequent generations, do children inherit the same disease risks their parents have?
        3. Did the Punnett square help predict what genotype the child got?

        7. Optional Extension Activities:

        1. Suppose that their patient couples had ten children. Have students roll the die to determine the children's genotypes for each disease. Ask students to determine the proportion of the children with each genotype. Did the proportions match the Punnett square predictions? Why or why not?
        2. Have students consider personal and public genome sequencing. First, visit the Web site of a company that will perform DNA analysis, such as 23andMe. Then, visit the Web site of a genetics research project, such as the Personal Genome Project. Ask students to discuss whether or not they would want to know their own genetic risks for particular diseases or if they would allow their genetic information to be used for research.
        3. Have students research genetic counseling careers, starting with the National Society of Genetic Counselors

        Check for Understanding

        Discuss what are the pros and cons of discovering a person's genotype for a particular disease. You can also use the answer key and rubric in the Teacher Notes—Risky Genetics PDF Document to assess each student's work on the lesson and the handout.


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