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Fixing the Leaning Tower of Pisa

All in the Family

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Eruption!

Where's the Matter?

Renaissance Machines
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TEACHING GUIDES


SCIENCE ITALIAN STYLE: All in the Family


An uncertain future awaits the Abruzzo brown bear and chamois, two subspecies of endangered wildlife. Before beginning a captive breeding program, biologists conduct a bear census and do DNA analysis to ensure species uniqueness. Many chamois in one park must relocate and are airlifted to other areas, where biologists hope that time and evolution will build up diverse populations. As wildlife conservationists learn, sometimes the programs intended to save animals create unexpected risks.

Curriculum Links
Activity: Close, Closer Closest
Consider This!



CURRICULUM LINKS

BIOLOGY

DNA, evolution,
genetics, pedigree
CHEMISTRY


organic molecules
EARTH SCIENCE

ecosystems
ECOLOGY


endangered species, habitat destruction


LIFE SCIENCE

animal behavior,
biomes, mammals,
taxonomy
MATH



probability
PHYSICAL SCIENCE


radio signals
SOCIAL STUDIES

cartography, contemporary issues
TECHNOLOGY



DNA analysis



ACTIVITY: CLOSE, CLOSER, CLOSEST

An animal's genetic makeup can be analyzed using a technique called restriction mapping. In this process, strands of genetic material are first attacked by enzymes that cleave the DNA at specific sites. Next, the fragments resulting from this cleavage are sorted in a chromatography-like process called electrophoresis. If samples from two organisms contain a similar assortment of DNA fragments, then the organisms are closely related. If fragment concentrations are dissimilar, the organisms are less related. In this activity, you will perform an experiment that models this type of DNA analysis.

MATERIALS
  • mock DNA solutions
  • coffee filters or paper towels
  • scissors
  • straw
  • container for water
  • paper clips


PROCEDURE
  1. Cut coffee filters into five strips, each about 1cm wide and 10cm long.

  2. Using a toothpick, transfer a drop of one DNA mock solution to one of the strips. Place the drop in the middle of the paper strip, about 2cm above the lower edge. Let the solution dry.

  3. Repeat Step 2, using a different strip of filter paper for each of the mock DNA solutions.

  4. Place a paper clip on the upper edge of each strip. Then, slide a straw through the clips. The strips should hang freely.

  5. Pour about 1cm of water into the container.

  6. Position the straw over the container so that the strips contact the water (the dots should be about 1cm above the surface of the water).

  7. After 15 minutes, examine the strips. Compare your strips with other samples in your own collection and with samples of other students.


LAB NOTES

This activity can be performed by individuals or in groups. Make five mock DNA solutions using food coloring; three should be similar and two dissimilar. Each group or individual should have one sample of each of the five solutions.

QUESTIONS
  1. What happens to the sample drops?

  2. Which samples have a similar makeup?

  3. Which samples appear dissimilar?

  4. How can you apply your observations to restriction mapping?


ANSWERS
  1. They separate into colors as they travel up the paper.

  2. Answers will vary.

  3. Answers will vary.

  4. Like solutions of DNA fragments, the food-coloring solutions separate into components. Similarities and differences in the components are then used to classify the solutions. Solutions that show similarities are analogous to restriction mapping of closely related species; dissimilar solutions represent distant relations.




CONSIDER THIS!
  • It is estimated that more than 99% of the species ever living on Earth are now extinct. How much should people do to preserve living species?

  • Should endangered species always be rescued, despite the risks? Who should determine which species are saved?

  • Why is inbreeding a serious problem? How has inbreeding affected the cheetah?









 

Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
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