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NOVA scienceNOW: Stem Cells Breakthrough

Viewing Ideas

Before Watching

  1. Explore terms related to stem cells. Have student pairs match cell and genetics terms to their definitions. Read aloud a definition and see if students can name the corresponding term. Or, say the term and ask for a definition. Alternatively, delete the "Term" column from the table below, then photocopy and distribute the "Definition" column, one per student pair. Write the terms on the board and have pairs match them to the definitions on the table.

    Term Definition
    Differentiation The process by which specialized cells and tissues develop from common, unspecialized ancestor cells, such as stem cells.
    DNA Deoxyribonucleic acid, the molecule that controls inheritance.
    Embryonic stem cells Stem cells obtained from a blastocyst.
    Gene The basic unit of inheritance. Genes control the production of proteins.
    Genetics The study of genes and their relationship to characteristics of organisms.
    Genome An organism's basic complement of DNA
    Stem cells Unspecialized cells that are able to divide indefinitely and that have the potential to develop into different types of cells, such as muscle, nerve, bone, or heart cells.
    Pluripotent Capable of differentiating into all of the various cell types that make up the body.
    Totipotent Capable of developing into a complete organism or differentiating into any of its cells or tissues
    Multipotent Capable of differentiating to several specialized cells or tissues of an organism.
    Adult stem cells Undifferentiated cells found in a differentiated tissue that can give rise to all the specialized cell types of the tissue from which they originated. Their main role is to repair the tissue or organ they are in.
  2. Preview the concepts in the video by viewing NOVA scienceNow's previous segments on stem cells. Show your class the 2004 Stem Cells program (, which examines embryonic stem cell research, cloning, and the ethics surrounding the use of embryonic stem cells. A 2006 update segment ( is also available for viewing.

  3. Model the development of stem cells. Either from reference books or online, obtain pictures showing the stages of embryonic development. (See the Links & Books section for suggested references.) Explain to students they will be working in teams, using clay or making drawings to model the development of different types of stem cells. If necessary, review the definitions of totipotent, pluripotent, and multipotent (see Before Viewing activity #1). Group the students into teams, and give each team several colors of clay (or drawing materials) and pictures of the following stages: zygote, early cell division (2-16 cells), morula, blastula, and gastrula. Have students create a separate clay model or drawing for each stage of development. You might suggest that they use different colors to represent the outer layer of the blastula stage and the three layers of the gastrula stage (endoderm, mesoderm, and ectoderm). After students have completed their models, explain that the cells of different stages have different potencies. (The cells of the zygote, early cell division, and morula stages are totipotent cells. The cells of the blastula stage are pluripotent. The cells of the gastrula stage are multipotent.) Also discuss how different stages relate to different types of stem cells. (Cells of the blastula stage are the source of embryonic stem cells, while cells of the gastrula stage are considered adult stem cells and can only make the type of cell determined by the cell's layer: The endoderm cells can become the digestive and respiratory tracts; the mesoderm cells can become bones, blood cells, and the heart; and the ectoderm cells can become the skin and central nervous system.)

After Watching

  1. Simulate the use of "knockouts" to investigate gene function. Shinya Yamanaka, George Daley, and Rudolph Jaenisch all identified three to four genes that are needed to reprogram skin cells into stem cells. In the segment, genes that can "reprogram" skin cells are inserted into them to produce stem cells. One technique researchers use to identify these reprogramming genes involves knockouts. Knockouts are organisms or cells that have been engineered with inoperative genes. Researchers use them to investigate gene function by examining differences between the functioning of knockouts and that of a normal organism or cell.

    Divide the class into teams. Explain that each team is a group of scientists working on cell programming. Tell students that they will be given two sets of letters, one that represents a skin cell and one that represents a stem cell. (Note: The sets of letters are not intended to indicate actual genes.) They will also be given sets of letters that represent various knockouts. Each team's job is to identify which knockouts can be used to transform the skin cell into a stem cell. Supply each team the following information:

    Genes needed for Stem Cell: A F N

    Active Skin Cell Genes: A B C E F G I J K M N O

    Knockout Operative Genes in the Knockout Genes that have been made inoperative (knocked out) of the skin cell Candidate for Stem Cell? Yes/No
    A B C E F   I J K     O
    G M N No—stem cell needs N
      B C E   G   J K M N O
    A       F G I J K M N O
    A B C E   G I     M N O
    A B C E F     J K   N O
    A B C       I J K M N O
    A B C E F G I J   M    
    A B C E F G I     M N  
      B C E   G I J K M   O
        C E F   I J K M N O

    First have students complete the third column by comparing each Knockout set to the Skin Cell to identify which "genes" have been made inoperative, in the Knockouts. For example, in Knockout 1, the G, M, and N "genes" are inoperative, while in Knockout 2, the A, F, and I "genes" are inoperative. Next, have students complete the right-hand column by determining which Knockout or combination of Knockouts contain the "genes" that can be used to transform the Skin Cell into the Stem Cell. (Answer: Three Knockouts–Knockouts 3, 5, and 8–contain genes that need to be combined to transform the Skin Cell into the Stem Cell. The other Knockouts have at least one gene essential to the Stem Cell that is inoperative.) When students have completed the activity, discuss the results as a class. How is this activity similar to the actual method used to produce induced pluripotent stem cells? How is it different? (Normal skin cells have approximately 20,000 genes, and each knockout is usually engineered to disrupt only 1 gene [rather than 3, as is done in this activity]. The knockouts are used to identify gene function. Once genes that can "reprogram" the skin cell have been identified, they are inserted into the cell to produce stem cells. Shinya Yamanaka, George Daley, and Rudolph Jaenisch all identified 3-4 genes that can reprogram skin cells into stem cell.]

  2. Compare different methods of obtaining stem cells. Point out to students that Shinya Yamanaka developed a new method for producing stem cells. Ask students to research the steps involved in generating a stem cell line (a) from an embryo; (b) by cloning; and (c) from adult tissue. Have students make diagrams or flow charts outlining each method. Ask them to identify the advantages and disadvantages of each. As an extension, discuss the political and ethical issues related to the creation of stem cell lines for research.

  3. Research ways in which stem cells could be used to treat diseases or conditions. Explain to students that researchers are exploring stem cell-based treatments for a variety of diseases and conditions. Have teams of students select one of the following to research: sickle-cell anemia, multiple sclerosis, stroke, muscular dystrophy, Parkinson's disease, or leukemia. Have each group prepare and present a poster that includes the following about the disease or condition they've selected:

    • The causes of the disease, if known
    • The symptoms of the disease
    • Current treatment possibilities and the risks associated with such treatments
    • How stem cells could be used to treat and/or cure the disease, along with any risks associated with such treatment

    After students have completed their posters, have the teams share them with the class.

Links and Books

Web Sites

NOVA scienceNOW
Offers resources related to stem cells, including additional activities, streamed video, and reports by experts.

Frequently Asked Questions on Stem Cell Research
Answers questions about stem cells, such as what they are and how they are used.

Florida Institute for Reproductive Sciences and Technologies
Includes video and images of the stages of embryo development.

HHMI: Potent Biology: Stem Cells, Cloning, and Regeneration
Presents holiday lectures on topics related to embryonic and adult stem c

Stem Cells at the National Academies
Offers information about stem cells and includes the National Academies downloadable booklet "Understanding Stem Cells: An Overview of the Science and Issues."

Stem Cell Information
Provides a comprehensive online resource on the science and ethics of stem cells, including sections on scientific research and the treatment of diseases.

Stem Cell Network
Provides information on stem cell research pertaining to 20 common diseases. Also provides background information on the diseases.

Understanding Genetics: Human Health and the Genome
Offers a series of articles by geneticists that explain the basics of stem cells, along with recent stem cell discoveries and controversies.


Human Embryonic Stem Cells: An Introduction to the Science and Therapeutic Potential
by Anne Keissling.
Jones and Bartlett Publishers, 2003.
Provides information on human embryonic stem cells and the diseases that may be treated by stem cell therapy, as well as a historical overview and the scientific details necessary for understanding the overall biology. Also examines the many moral and ethical issues surrounding this field of research.

Stem Cells: Scientific Progress and Future Research Directions
by National Institutes of Health.
University Press of the Pacific, 2004.
Explores some of the cutting-edge research featuring stem cells.

The Proteus Effect: Stem Cells and Their Promise for Medicine
by Ann B. Parson.
Joseph Henry Press, 2004.
Chronicles the history of stem cell research, explores the ethical debates, and examines the use of stem cells for therapeutic medicine.

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: Stem Cells Breakthrough