Collect Your Own DNA

Collect Your Own DNA!

Materials: Small cup 6% salt solution (1 T salt to 8 oz.) or a mouthful of gatorade Test tube 10% soap solution (1 part soap to 9 parts water) Alcohol

Procedure: 1. Pour 15 mL of salt water or gatorade solution into the cup.

2. Put the solution into your mouth and swirl it around your mouth for 30 seconds. REMEMBER: MORE VIGOROUS SWIRLING COLLECTS MORE CHEEK CELLS!

3. Spit the water back into the cup.

4. Pour enough of the swirled salt water into the test tube to fill it up half way.

5. Add 2 mL of soap solution and mix by swirling gently 3-4 times.

6. Add about 2 mL of ethanol. Pour it gently in along the side of the test tube so it forms a layer on top of the salt water or gatorade/soap solution.

7. Wait one minute.

8. Hold the test tube up to the light and look for the cloudy, stringy substance forming at the bottom of the alcohol layer. You may see a cloud of bubbles. As the bubbles rise to the surface, you will begin to see white “strings” being drawn up along with the bubbles. These “strings” are clumps containing thousands of DNA molecules.

9. Take a glass rod and put it all the way into the test tube and turn it in one direction. DO NOT STIR! The DNA will wrap around the rod.

How it works: Cells contain water, proteins and nucleic acids (DNA and RNA) within a membrane made of lipids (fat). When you add soap, it breaks the membranes open and the contents of the cell spill out. The salt changes the ionic concentration of the water and makes it easier for the DNA and RNA to separate. DNA will not dissolve in alcohol, so when you add it to the solution, the DNA collects where the two layers meet.