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Growing body parts may sound like science fiction, but scientists are already hard at work on doing just that in the lab. The search is on for a source of human cells that can be cultivated to replace or repair damaged or diseased hearts, lungs, eyes, skin and other tissues. Tools and techniques of biotechnology hold great potential and promise in this century.

Curriculum Links
National Science Education Standards
Discussion: The Biotech Era
Activity: DNA Model



cells, DNA



(Please visit the Subject-Area Search feature on this website for related Frontiers shows and activities!)


5-8: Structure and Function in Living Systems; Reproduction and Heredity
9-12: The Cell; The Molecular Basis of Heredity; Matter; Energy and Organization in Living Systems
5-8, 9-12: Understandings About Science and Technology
5-8: Personal Health; Science and Technology in Society
9-12: Personal and Community Health; Science and Technology in Local, National and Global Challenges
5-8: Science as a Human Endeavor; Nature of Science; History of Science
9-12: Science as a Human Endeavor; Nature of Scientific Knowledge; Historical Perspectives


Many health problems could be solved if our bodies could grow whatever is needed to replace diseased or damaged parts, from heart muscle to blood cells, even neurons.

To accomplish this goal, scientists are working to cultivate stem cells -- the blank, undifferentiated cells that can grow into cells that perform specialized functions. For example, if stem cells could develop into neurons (brain cells), a person with Parkinson's disease could use stem-cell therapy to heal the brain.

In this episode of Frontiers, you see how scientists implant the nucleus of a mature human skin cell into a cow egg, where the mature cell is then transformed into a stem cell. The goal of this research is to one day create custom-made replacements for body parts lost to aging, disease or injury -- replacements that would be a perfect tissue-match to whatever mature cell is used for the implant. Such custom parts would solve the critical shortage of organ donors, while eliminating the problem of organ rejection.

Imagine being able to grow your own kidney to replace a damaged or diseased one. As you'll see in this episode, what sounded like science fiction in the field of tissue engineering may become reality very soon in the 21st century.


All living things, from plants to people, are individually coded with information found in the genes stored on DNA. Genes are bundles of DNA that instruct cells to produce vital proteins.

DNA or deoxyribonucleic acid is shaped like a twisted spiral staircase with about 3 billion rungs. The uprights of the ladder are alternating sugar and phosphate groups; the rungs are made of paired nitrogen bases. Instructions are written on the bases in a chemical code using the letters A (adenine), G (guanine), C (cytosine) and T (thymine) to represent DNA's chemical makeup. Adenine always pairs with thymine; guanine always pairs with cytosine. The order in which these bases are arranged codes for specific genetic traits. If the letters are changed, mutations can arise. In this activity you'll create a model of DNA.


  • tag board or other light cardboard
  • scissors
  • colored pencils or markers
  • tape

  1. Photocopy or draw the puzzle shapes shown above onto cardboard and cut them out. (You may wish to enlarge them on a photocopier.) You will need at least five of each puzzle shape.

  2. Color the tips of the nitrogen bases as follows:

    • adenine = red
    • thymine = yellow
    • guanine = green
    • cytosine = blue

  3. Construct one side of the DNA ladder by randomly lining up five of the puzzle pieces and taping them together.

  4. Color the uprights alternating colors: orange and purple. The orange represents sugar groups and the purple represents phosphate groups.

  5. Use your remaining pieces to complete the opposite side of the ladder. Make sure the base pairs match up correctly.


  1. Debate the ethical and social implications of tissue engineering, stem cell research, xenotransplantation, cloning and other biotechnologies.

  2. Brainstorm some of the potential applications of the medical breakthroughs seen in this episode of Frontiers, especially the possibilities for tissue engineering in this story.


Scientific American Frontiers
Fall 1990 to Spring 2000
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