Cheek Cell DNA Extraction Lab
Overview
Instructions on how to extract DNA from students cheek cells. Includes follow-up questions.
DNA:Parts & Processes
DNA:Parts & Processes Name_____________________ Date________per____ |
Cheek Cell DNA Extraction
Objective To extract and examine your very own DNA!
Background DNA (Deoxyribonucleic Acid) is the molecule inside all living organisms that carries that organism’s genetic information. In humans, DNA is found in almost all cells types: skin cells, muscle fibers, reproductive cells, and many others. The exception to this rule is red blood cells. Mature red blood cells have lost their nuclei and therefore do not have DNA.
Materials
Dixie cup with salt-water solution (500mL/4.5g NaCl)
Detergent (soap) solution (50mL/450mL H2O)
Plastic bulb pipets or eye droppers
Test tube with stopper or cap
Test tube rack
Wooden skewer or toothpick
95% ethanol
Procedure
- Into your test tube, add 5 ml detergent solution.
- Gently chew on the insides of your cheeks for a moment or two.
- Grab a Dixie cup with salt-water solution.
- Swish the salt-water solution in your mouth for at least 30 seconds. Swish vigorously, like you would with mouthwash. Do not swallow the salt-water! The more you swish, the better your results will be!
- Spit your swished water back into your Dixie cup.
- Pour your salt-water/spit into your test tube.
- Stopper your test tube and GENTLY rock the tube back and forth for two minutes. Be careful - vigorous shaking will “shear” (rip) the DNA.
- Tilt your test tube slightly and GENTLY and SLOWLY pour 5 ml of ethanol down the inner wall of the test tube.
- Wait 5-10 minutes.
- You should see a layer of white, stringy mucous-like material. This is your DNA!
DNA Extraction, Continued….
What’s happening here? Think for a moment about what you did in the procedures, and then read the paragraph below.
Each cheek cell is surrounded by a plasma membrane composed of lipids (fats) and proteins. The soap breaks apart the plasma membrane and also the membrane around the nucleus inside each cell. DNA is a polar molecule – it has a slightly negative charge. It dissolves in the salt solution.
The fats, carbohydrates, and proteins do not dissolve in the salt-water and settle out of solution. Adding alcohol precipitates the DNA molecules because DNA does not dissolve in alcohol.
Therefore, it clumps up into the white stringy material you can see. What you see is DNA from many cells. Each cell in your body contains about 6 feet of DNA that is only about one-millionth of an inch wide!
Now answer the questions below:
- What does your DNA look like?
- Why did you swish your mouth with salt water?
- Why did you mix your spit with soap?
- Why did you add the alcohol?
Please pour the contents of your test tube in the sink and place your test tube in the bleach bucket. Thanks for cleaning up your lab space!