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NOVA scienceNOW: Personal DNA Testing

Viewing Ideas

Before Watching

  1. Research and categorize medical conditions that affect human health. Provide students with a list of diseases and medical conditions they have heard about. Introduce and explain the categories preventable, treatable, and curable to the class. Then have pairs each research a different condition/disease and classify it into its current accurate categories. Explain that the categories for diseases may change as new medical knowledge is gained.






    X (some types)


    X (some types)

    Bipolar disorder









    X (some types)


    X (some types)

    Heart disease









    X (some types)


    X (some types)





    Multiple sclerosis




    Sickle cell disease












    Explain to students that medical tests can often reveal the likelihood that a person will get a disease or condition. If they could find out, would they want to know their risk? Is it better to know one has a high risk of getting a disease or would that knowledge negatively impact one's quality of life? How would knowing whether the disease is preventable, treatable, or curable make a difference in wanting to find out?

  2. Use a concept map to review the concept of genetic inheritance. Concept maps visually show how the parts of a system relate to one another. Copy and cut apart the terms below. Distribute sets to student pairs or small groups. Have students find the definitions for the terms using dictionaries, textbooks, or other resources, such as the Internet. Then have students create a concept map that shows the relationship between the words by asking them to position the different terms on a piece of paper and draw arrows linking the terms. Ask students to label each arrow with a term or phrase describing the relationship between the components. (You may do this activity as a class and have students share their reasoning for each connected word. An example might include: mutations include deletions and substitutions.)







    Sexual reproduction









    Genetic variation





    Gene expression

  3. Model mathematical expressions of risk. Discuss the concept of probability with the class. Define probability as how likely or unlikely it is that something will happen. Ask students to describe situations where they've heard the people use the terms probability, chance, likelihood, or risk when talking about health issues. If necessary, provide an example to start the discussion, such as "the American Cancer Society reports that for women ages 40-59 the risk of developing breast cancer is 1 in 24." Record student responses on the board.

    Remind students that the probability of an event happening is expressed as a fraction or decimal from zero to one. Zero probability means the event will not happen; one means it is certain to happen. Demonstrate this concept by putting different-colored marbles (or jelly beans) into a bag or opaque jar. Have students use the following equation to calculate the chances of selecting a marble of a particular color.

    Number of chances possible for the event
    (e.g., the number of a certain color marble)
    Number of total chances
    (e.g., the total number of marbles)

    Ask students to answer the following questions using the marbles and the probabilities they calculated. In the example below, the jar has ten red, six blue, and four green marbles.

    1. What is the probability of choosing each color?

    2. List the colors in order from least likely to be picked to most likely to by picked.

    3. Which color would you expect to pick first? Why?

    4. Without looking, take out one ball. What color is it? Is it the color you predicted?

    5. Put the ball back in the jar. Then again, without looking, take out one ball. What color is it? Is it the color you predicted? Repeat 8 more times.

    6. Does having a high probability of getting a particular color mean that you will definitely get that color? Why or why not?

    7. Does having a low probability of getting a particular color mean that you will definitely will not get that color? Why or why not?

    (Answers based on example: 1. (½, 0.5, or 50% red), (3/10, 0.33, or 33 1/3% blue), (2/10, 0.2, or 20% green); 2. green, blue, red, 3. red, because there is a higher probability; 4. answers will vary; 5. answers will vary; 6. no, because probability indicates chance, not certainty.; 7. no, because probability indicates chance, not certainty.)

After Watching

  1. Investigate how single nucleotide polymorphisms (SNPs) are used to determine genetic risk. Remind students that single nucleotide polymorphisms (SNPs) are DNA sequence variations that occur when a single nucleotide in the genome sequence is altered. For example, a SNP might change the DNA sequence CAGTAG to CTGTAG. SNPs can help determine the likelihood that someone will develop a particular disease. Explain that by looking at a number of SNPs in a particular region of DNA, scientists can group people into what are known as haplotypes. People with the same SNPs in that region are placed in the same haplotype group. Different haplotype groups have different probabilities of getting a particular disease or condition.

    Divide the class into teams and give each a copy of the Genetic Testing for Diabetes student handout. Explain that the students are working for a genetic testing company and will be using SNPs to determine if patients are: 1) at risk for getting diabetes; and 2) if so, the likelihood of the patient getting the disease. Have students work in pairs or small groups to complete the worksheet. Once all the groups have finished, discuss the answers as a class.

    (Answers: 1. Patient 1 and Patient 2 have markers for diabetes. 2. Patient 1, Group 4, Patient 2, Group 1, Patient 3, Not Applicable. 3. Patient 1: 20-40 percent risk. Patient 2: greater than 80 percent risk.)

  2. Conduct a survey. Have students discuss the implications of the genetic testing described in the show. What is the value of genetic testing? What are some of the potential personal, legal, and/or ethical problems with testing? Together with students to generate a list of potential anonymous survey questions to find out people's opinions on these issues. Direct them to consider the following questions as a model for the survey questions:

    • Would you want to be tested for a gene that increases your risk for a disease but does not determine whether you will actually develop it?

    • Would you want a family member to be tested for a gene that shows an increased risk for a disease but does not determine whether he or she will actually develop the disease?

    • Would you want to be tested for a gene that determines that you will develop a disease, assuming the disease is preventable?

    • Would you want to be tested for a gene that determines that you will develop a disease, assuming the disease is curable?

    • Would you want to be tested for a gene that determines that you will develop a disease, assuming the disease is treatable but not curable?

    • Would you want to be tested for a gene that determines that you will develop a disease, assuming the disease is neither treatable nor curable?

    • Would you want yourself and your partner to be tested before having children to determine whether you were both carries for a disease, in which case you are at high risk for having a child who contracts the disease?

    • Should unborn children be tested for genetic problems and/or diseases?

    • Should employers have access to your genetic information?

    • Should insurance companies have access to your genetic information?

    After students have completed the survey questionnaire, group the students into teams, and have each team conduct the survey both at school and at home. Tally and discuss the results in class.

  3. Design a brochure about a genetic disease or condition. Have teams of students research information about genetic diseases/conditions such as Alzheimer's Disease, breast cancer, colon cancer, glaucoma, or heart disease, for which genetic tests are currently available. (See Links and Books for resources for student research.) Ask each team to select one disease or condition and create a brochure about the disease's causes, symptoms, and possible treatments. Have them include information about the genetic tests that are currently available for that condition or disease and what information those tests actually provide (i.e., probability of risk versus actually having the disease). After students have completed their brochures, have the teams share them with the class.

Links and Books

Web Sites

NOVA scienceNOW
Offers resources and activities related to personal genetic testing.

The Basics on Genes and Genetic Disorders
Describes basic information on genes, heredity, genetic disorders, genetic engineering, gene therapy, and the Human Genome Project.

Genetics Home Reference
Includes information on more than 300 genetic health conditions, diseases, and syndromes; a handbook with chapters on inheritance, genetic testing, counseling, and more; as well as a glossary, databases of genes and chromosomes, and a resource page.

The Genomic Revolution
Explores the ethical, social, cultural, and medical issues surrounding the latest discoveries in the field of genomic science.

Glossary of Genetic Terms
Provides definitions, pronunciations, audio information, images, and additional links to related genetics terms.

HHMI: Personal DNA Testing
Presents HHMI resources releated to genetic testing.

SNP Fact Sheet
Contains basic information on SNPs, how they are used in genetic testing, and links to articles and tutorials on SNPs and medical conditions.


Cracking the Genome: Inside the Race to Unlock Human DNA
by Davies, Kevin.
The Free Press, New York: 2001.
Chronicles the decoding of the human genome, from the discovery of the double helix in the 1950s to the White House announcement in June 2000 that the first draft of the sequence was complete.

Decoding Life: Unraveling the Mysteries of the Genome.
by Fridell, Ron.
Lerner Publishing Group, Minneapolis, MN: 2004.
Describes cutting-edge research and discoveries in genetics and discusses ethical issues regarding genetic privacy, genetically modified children, and human cloning.

Medicine's Brave New World: Bioengineering and the New Genetics.
by Hyde, Margaret, and John Setero.
Lerner Publishing Group, Minneapolis, MN: 2001.
Presents a number medical breakthroughs and ponders the future of many versions of genetic manipulation to support medical science. Topics include fertility advances, xenotransplants (the transfer of animal organs or cells to humans), stem cell research, cloning, the Human Genome Project, and genetic testing.

Activity Author

Margy Kuntz has written and edited educational materials for more than 24 years. She has authored numerous educational supplements, basal text materials, and trade books on health, science, math, and computers.

Teacher's Guide
NOVA scienceNOW: Personal DNA Testing

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