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Eat Less -- Live Longer

The Clock of Life

Wisdom of the Worms

How to Make a Nose

Use It or Lose It

Viewer Challenge

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TEACHING GUIDES


Never Say Die:
Wisdom of the Worms


Could microscopic roundworms hold the key to a long life? San Francisco researcher Cynthia Kenyon has been studying a primitive roundworm, the nematode known as C. elegans. Random mutations in long-lived nematodes led Kenyon's team to some amazing discoveries that may provide more clues about extending the aging process in people.

Curriculum Links
National Science Education Standards
Activity: Kitchen DNA




CURRICULUM LINKS


BIOLOGY/
LIFE SCIENCE


DNA

GENETICS


HEALTH



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




NATIONAL SCIENCE EDUCATION STANDARDS

SCIENCE AS INQUIRY / LIFE SCIENCE
5-8: Structure and Function in Living Systems; Reproduction and Heredity
9-12: The Cell; The Molecular Basis of Heredity; Biological Evolution; Matter; Energy and Organization in Living Systems
SCIENCE & TECHNOLOGY
5-8, 9-12: Understandings About Science and Technology
SCIENCE IN PERSONAL & SOCIAL PERSPECTIVES
5-8: Personal Health; Science and Technology in Society
9-12: Personal and Community Health; Science and Technology in Local, National and Global Challenges
HISTORY & NATURE OF SCIENCE
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




ACTIVITY: KITCHEN DNA

The life span for every species differs. Moths live about two weeks, while Galápagos tortoises can live to 150 years and, unlike most other animals, show no signs of aging. These and other genetic puzzles are providing many research opportunities for scientists in biotechnology.

In this story, you'll meet genetic pioneer Cynthia Kenyon, whose mutating nematodes could hold some of the keys to living much, much longer. Because the nematode C. elegans is similar to humans at the cellular level, Kenyon's findings may offer insights into the way genes regulate aging in people. Kenyon theorized that something in the genes influences the length of time each animal lives. She began to study a small nematode, the roundworm C. elegans. Kenyon found that mutated genes enabled some nematodes to live much longer than others. Not only did the roundworms live longer, but they also behaved and looked younger. Kenyon's findings may offer insights into the way genes regulate aging in people.

The C. elegans nematode, with about 20,000 genes and 97 million base pairs of DNA, is simpler to decode, compared to one person's more than 100,000 genes on three billion base pairs of DNA. The C. elegans roundworm is the first multi-celled organism to have its genome completely mapped (see elegans.swmed.edu/genome.shtml). In 1999, scientists working to map the human genome announced that they had sequenced one billion base pairs of DNA.

Before they can study genes, biologists first have to extract DNA. In this activity, you'll view actual DNA after isolating it from onion cells.

MATERIALS

  • blender
  • 1 cup cold water
  • 1/8 tsp. salt
  • 1 small onion (peeled)
  • strainer
  • flat toothpicks
  • paper coffee filters
  • 2 tbsp. clear liquid dish soap
  • powdered meat tenderizer
  • 1/8 cup isopropyl rubbing alcohol (chilled)
PROCEDURE
  1. Dissolve the salt in the water. Cut the onion into quarters.

  2. Combine salt water and the onion in the blender and blend for about ten seconds (some small pieces of onion will remain).

  3. Transfer the mixture to a separate plastic container and add the 2 tbsp. dishwashing soap. Stir gently with a toothpick; try not to create any bubbles.

  4. Place the coffee filter into a wire strainer and place an empty cup underneath. Pour the onion mixture into the strainer, allowing the liquid to seep through. You should have about 1/2 to 1 cup of liquid. (Dispose of whatever remains in the coffee filter.)

  5. Add a pinch of meat tenderizer to the liquid and stir gently with the toothpick.

  6. Carefully pour 1/8 cup chilled isopropyl alcohol into the mixture. The DNA will rise into the alcohol layer (it will look stringy and bubbles may be attached to it). Use a toothpick to extract the long stringy DNA from the liquid. This is onion DNA! (You can only see the double helix pattern of DNA in an electron microscope.)

EXTENSIONS

  1. Investigate how each of the substances used helps extract DNA from cells. Detergent and salt break down lipids (fats) in the cell membrane. Salt removes water from within the cell. Meat tenderizer contains an enzyme called papain that helps clean protein from the DNA that may otherwise contaminate it. Alcohol (ethanol works even better) helps the DNA uncoil and precipitate.

  2. Investigate the role of insulin in the body. Insulin is one of the chemicals derived from food, so animals on a calorie-restricted diet may benefit from lower insulin levels. Modifying diet modifies insulin. Follow this line of thinking, based on what you see on Frontiers.

  3. Discuss the ethical issues involved in genetic engineering. If a mutation for a short or long life span is identified, does this mean the knowledge should be used?

  4. You can also do this DNA experiment with animal cells. Try using chicken or beef liver or a beef thymus (sweetbreads). Compare the DNA by studying it under a microscope. You might also investigate and compare plant DNA.

  5. Compare the natural life spans of various species. Explore the evolutionary advantage of human longevity. Why do humans live so long, compared to other species that die soon after reproduction?






 

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