Experiment objective

Extract DNA from any living thing

Read more background about this activity in Sid Altman's bio...

You need

  • Your DNA source (say 100ml or 1/2 cup of split peas. You can also use an onion, a banana, or even saliva from your mouth.)
  • A large pinch of table salt (less than 1ml or 1/8 teaspoon)
  • A cup of cold water
  • A blender
  • A strainer
  • Some detergent (about 15ml or a tablespoon)
  • Enzymes (a pinch of meat tenderizer, pinapple juice, or contact lens cleaning solution)
  • Alcohol (isopropyl, ethyl, or 70 - 95% rubbing alcohol)
  • Wooden stick

1. Put the peas, salt and water into a blender and blend on high for 15 seconds. This breaks all the cells.

2. Pour the pea mixture through a strainer into another container (like a measuring cup).

3. Add liquid detergent and swirl to mix. Let the mixture sit for 5-10 minutes.

4. Pour the mixture into test tubes or other small glass containers, each about 1/3 full.

5. Add a pinch of enzymes to each test tube and stir gently. Be careful! If you stir too hard, you'll break up the DNA, making it harder to see.

6. Tilt your test tube and slowly pour rubbing alcohol into the tube down the side so that it forms a layer on top of the pea mixture. Pour until you have about the same amount of alcohol in the tube as pea mixture.

7. DNA will crystallize and form right at the boundary of the alcohol layer and the pea water layer. You can use a wooden stick or other hook to draw the DNA into the alcohol and out of the test tube. It should look like long wet clumpy threads.

NOTE: This experiment was adapted and the image borrowed from the Genetic Science Learning Center at the Eccles Institute of Human Genetics, University of Utah