ScienceMakers Toolkit Manual - The History Makers

Life Science
Experiment - See Your Own DNA
This lesson was adapted from educational materials developed by the Center for the Advancement of Science
Education at the Museum of Science and Industry.
You will need four 8-ounce containers.
1. In one container, mix a full glass of water with 1 tablespoon of table salt.
2. In the second container, mix 2 tablespoons of water and 1 tablespoon of Liquid Dish Soap.
3. Fill the third container half full with 70% Isopropyl (rubbing) alcohol.
4. Take approximately one tablespoon of the salt-water solution from the fi rst container and swirl it in your
mouth for 30 seconds.
5. After 30 seconds spit the salt water and whatever contents are moving around in your mouth into the fourth
container that was still empty.
6. Pour just enough of the spit solution to fi ll the top of the test tube. NOTE: Do not pour all of that swirledspit
into the test tube! The rest should be disposed of when you are fi nished.
7. Add 1 teaspoon of the soap-water solution to your test tube of spit. Secure your fi ngers around the top of the
tube and move the solution around in a small circular motion for about one minute.
8. After you’ve rotated the spit, carefully fi ll the rest of the test tube with rubbing alcohol. When doing this,
pour the alcohol down the inside of the test tube, so the alcohol will form a separate layer on top of the
soap-spit mix. Wait about one minute, and you will see a cloud of bubbles hanging at the bottom of the layer
of alcohol. Those bubbles are attached to your DNA.
By swirling the salt water in your mouth, you collected a great deal of cells from the inside of your cheeks.
By spitting those cells (along with the salt water and saliva) into the test tube and mixing them with soap, you
were able to break up the outer membrane and nucleus of each cell. These cell membranes and the nuclear
membranes are made up of phospholipids (very similar to fats). The dish soap that you added dissolved these
phospholipids, thus exposing the DNA. This DNA then fl oats up through the soap until it hits the alcohol solution.
DNA is insoluble in cold alcohol, so it precipitates out of solution and forms the long white strands at the
bottom of the layer of alcohol.
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