1. DNA Extraction from Cheek Cells

2. Purpose • To view DNA from human epithelial cells

3. Background Where is the DNA located?

4. Cheek Cells • Cells from the lining of your mouth come lose easily. We will be able to collect cells containing your DNA by swishing a liquid around in your mouth.

5. Detergent Breaks open the cell and nuclear membranes, allowing the DNA to be released into the solution

6. O Na+ O P O Base Na+ O O CH2 Sugar O Na+ O O P Base Na+ O O CH2 Sugar OH Adding Salt • Na+ ions of NaCI bind to the phosphate groups of DNA molecules, neutralizing the electric charge of the DNA molecules. • The addition of NaCI allows the DNA molecules to come together instead of repelling each other, thus making it easier for DNA to precipitate out of solution when alcohol is added.

7. Adding Ice Cold Alcohol • DNA does not dissolve in alcohol. • The addition of cold alcohol makes the DNA clump together and precipitate out of solution. • Precipitated DNA molecules appear as long pieces of fluffy, stringy, web-like strands.

9. Procedure • Obtain a small cup of sports drink and swish it around in your mouth for 1 full minute. As you swish, gently and continuously scrape the sides of your cheeks with your teeth to help release your cheek cells. • Spit the drink (with your collected cheek cells) back into the small cup. • Pour the contents of the cup into your test tube (discard the cup).

10. Add 0.8 ml of NaCl and 0.8 ml of SDS solution to your test tube. • Place stopper on test tube and gently mix the contents. Do not shake the tube. • Add cold alcohol to the test tube and observe what happens between the layer of alcohol and cheek cell solution.

11. Discussion • What was the source of DNA in this lab? • What was the role of salt in this experiment? Explain. • What was the role of the detergent in this experiment? Explain. • What was the purpose of pouring cold alcohol over the cheek cell solution? • Would the DNA appear different if we had used plant DNA instead of human DNA?