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NOVA scienceNOW: Stem Cells

Viewing Ideas

Before Watching

1. Review stem cell-related vocabulary. Students should understand the following terms. Consider having them make a crossword puzzle with the terms.

   • Stem cells are able to divide indefinitely and have the potential to develop into different types of cells, such as muscle, nerve, bone, or heart cells. Theoretically, stem cells can divide forever to replenish other cells as long as an organism is alive. When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function. This capacity may make them valuable in treating diseases caused by the malfunction or degeneration of a particular kind of cell (e.g., Type 1 diabetes, cystic fibrosis, ALS—a.k.a. Lou Gehrig's disease, or muscular dystrophy).

   • Blastocyst (also Blastula): A hollow ball of cells that forms early in the development of an animal embryo—about four days after conception of an embryo.

   • Embryonic stem cells: Stem cells obtained from a blastocyst instead of from another source, such as tooth pulp, bone marrow, or an umbilical cord.

   • Differentiation: The process by which specialized cells and tissues develop from common, unspecialized ancestor cells, such as stem cells.

   • Mitosis: The kind of cell division that produces two diploid cells—cells with the same genetic information (i.e., number of chromosomes) as the parent cell.

   • Cloning: A term used by scientists to describe many different processes that involve making duplicates of biological material. Examine the topic of cloning by viewing the NOVA scienceNOW slide show, The Cloning Process.

   • Reproductive cloning: A process by which an embryo is created by nuclear transfer and implanted into a surrogate mother in hopes of bringing it to term.

   • Therapeutic cloning: A process by which an embryo is created through nuclear transfer in order to obtain stem cells from it for therapeutic and/or research purposes.

2. Identify student questions about stem cells and cloning. Often, students have misconceptions about stem cells and cloning. Identifying questions related to these misconceptions can be a powerful way to make students receptive to new information. On the board, write the following three column headings: Things I'm Sure About; Things I'm Fairly Sure About; and Questions I Still Have. Starting with the topic of stem cells, ask students to share what they have heard and to place their statement in one of the three categories. The intent is to identify the ideas students have rather than to answer the questions. The list of unresolved questions testifies to the fact that more information is needed to understand the issues. Repeat the exercise with the topic of cloning.

3. Model what nerve, muscle, and skin cells look like. In the video, scientists discuss the potential of embryonic stem cells to grow into any kind of body cell. Have students compare different kinds of body cells and relate them to stem cells. Give student teams some colored clays and pictures of stem, nerve, muscle, blood, and skin cells (from a biology book or the Web). Using the clay, have them make one of each kind of cell, highlighting what makes each cell type unique. Have students put their cell models on a central table. With the class around the table, point to a cell and ask students to write down what kind it is. After pointing to several cell models, have students compare answers to see if they were able to identify each cell type correctly. Ask them to list what each cell type has in common and what is unique to each cell type. Have students describe how each specialized cell type is adapted to its function. Remind students that all the cell types arose from stem cells. Have students discuss whether the ways cells are alike and different supports the idea of stem cells. As an extension, have students research what nerve, muscle, blood, and skin cells do and how each cell type's structure is related to its function. (This activity works well in conjunction with cell model-building activities that are often part of the biology curriculum.)

After Watching

1. Explore the ethics of stem cell research. No one is able to guarantee that stem cell research will lead to cures. Scientists want the freedom to work with stem cells but, as is typical with research, they cannot predict where such research will lead. Ask students (as a class, in groups, or individually) to answer one or more of the following questions and support their reasoning.

   • Researchers are unable to guarantee that their work with stem cells will produce beneficial results. How should this uncertainty influence the debate on whether scientists should be allowed to conduct such research?

   • Who should have jurisdiction over stem cell research (e.g., Congress, individual states, scientists, an independent agency, or the public)?

   • Kidneys secrete hormones, filter waste products from the blood, and help regulate the concentration of salts in the blood. Normally, people have two kidneys. However, some people lose the function of their kidneys. For people needing a kidney, doctors can transplant a new one if there is an appropriate kidney available. Unfortunately, there are not enough kidneys for everyone needing transplants. Kidneys are an example of an organ that researchers hope someday to be able to grow from stem cells. Discuss the reasons for and against growing kidneys from stem cells. (Reasons for include: increased availability; the recipient will not reject the new organ; no organ donor risk factors. Reasons against include: no guarantee of success from this research; objection to using embryonic stem cells; unforeseen problems with cloned kidneys; alternatives could exist, such as an expanded donor program.)

   • Certain diseases, such as Type 1 diabetes, Parkinson's, Alzheimer's, and ALS (Lou Gehrig's disease), are hard to study because the affected cells are damaged or destroyed before a patient knows he or she has the disease. Cloning cells derived from patients who have one of these diseases enables scientists like Doug Melton to watch the disease unfold in the laboratory. Seeing how cells fail gives researchers a better chance of understanding how such diseases start and of finding a way to stop them from developing. Many scientists think this aspect of cloning is even more important and far-reaching than simply making cells for transplants. Discuss the reasons for and against using embryonic stem cells to grow cell lines associated with a disease in order to better understand its onset and progression. (Reasons for include: understand diseases that begin years before symptoms are evident; reduces need to experiment on people; enables researchers to test drugs that might help stop the onset of the disease on cell lines rather than on people. Reasons against include: objection to using embryonic stem cells; no guarantee of success from this research.)

2. Take NOVA scienceNOW's online interactive poll that explores arguments for and against cloning for stem cell research. Compare your opinion with the views of other respondents.

Web Sites

Cloning/Embryonic Stem Cells
http://www.genome.gov/10004765
Discusses cloning, embryonic stem cells, ethical issues, and stem cell-related policy regulation.

Frequently Asked Questions on Stem Cell Research
http://isscr.org/science/faq.htm
Answers questions about stem cells, such as what they are and how they are used.

Stem Cell Research Policy Lesson Plan: Create an Advocacy Brochure
http://www.pbs.org/newshour/extra/
teachers/lessonplans/august01/stemcells/index.html
Provides a lesson in which students research stem cells and examine President Bush's ruling on federal spending for stem cell research.

Books

Burnie, David. The Concise Encyclopedia of the Human Body. New York, New York: Dorling Kindersley, 1995.
Contains information on cells, cell division, and blastocysts.

Oram, Raymond. Biology—Living Systems. Westerville, Ohio: Glencoe, Macmillan/McGraw-Hill, 1994.
High school biology text whose animal cells chapter includes a discussion of stem cells.