NOVA scienceNOW: Stem Cells
Review stem cell-related vocabulary. Students should understand the
following terms. Consider having them make a crossword puzzle with the
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
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
Reproductive cloning: A process by which an embryo is created by
nuclear transfer and implanted into a surrogate mother in hopes of bringing it
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.
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.
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.)
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
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.
Cloning/Embryonic Stem Cells
Discusses cloning, embryonic stem cells, ethical issues, and stem cell-related
Frequently Asked Questions on Stem Cell Research
Answers questions about stem cells, such as what they are and how they are
Stem Cell Research Policy Lesson Plan: Create an Advocacy Brochure
Provides a lesson in which students research stem cells and examine
President Bush's ruling on federal spending for stem cell research.
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