Using Genetic Evidence
DNA Extraction from Cheek Cells
adapted by Roxane Bonner
Laboratory of Molecular Systematics and Evolution University of Arizona
1. Vigorously swish 15 mL of Gatorade in your mouth for 30 seconds.
2. Chew on your cheeks while swishing so you get as many cells as possible.
3. Remember: more cells = more DNA!!! Spit the Gatorade back into your cup, then pour it into a new 15 mL plastic tube.
4. Mark your tube and lid with your initials. Find a partner and make sure your tubes each have the same volume.
5.Add more Gatorade if necessary to make the volumes equal. Place your tubes opposite each other in a centrifuge.
6. Spin the tubes on high for 3-5 minutes to collect cells at the bottom of the tube.
7. Pour the liquid into a waste container. Repeat steps #1-4.
8.Pour the Gatorade/Spit from your second mouthwash into the tube with the cells from your first mouthwash.
9. Add 2.0 mL of Lysis Buffer to the cell pellet. Mix by carefully flicking the tube. OPTIONAL .
10. Add 50 (l of Proteinase K (see teacher). Flick the tube to break up the cell pellet.
11. Incubate the cells at 65-70 C for atleast one hour, preferably overnight. Before proceeding, the solution should be clear and the cells should not be visible.
12. Add 1.0 mL of 5M NaCl. Mix well, then centrifuge for 10 minutes on high speed.
13.Transfer the liquid into a new 15 mL tube. Do not let the stuff on the bottom fall into the new tube. If necessary, use a clean pipet to transfer only the liquid.
14. Add 4 mL of cold 95% ethanol to the liquid in the new tube.
15. Mix well by rocking the tube gently back and forth until the DNA becomes visible. It should look like fine white fibers or lint.
DNA Extraction from Cheek Cells Directions:
Answer all questions in complete sentences.
1. How did we collect the cell pellets from the mouthwash solution?
2. Why do some people have larger cell pellets than others?
3. Why don't we see a cell pellet when we remove our tubes from the water bath?
4. What was the purpose of each of the following components?
The University of Arizona
Department of Biochemistry and Molecular Biophysics
General Biology Program for Secondary Teachers