HUMAN CHEEK CELL DNA EXTRACTION
The hereditary information (genes) for advanced organisms is stored in the nucleus of
cells. It is stored in the sequences of the nucleotide pairs located in the molecules of
DNA. There is an enormous amount of DNA in any cell. Amazingly, it is efficiently
stored in the nucleus and is visible during cell division as chromosomes. If all of the
DNA in a human body cell were stretched out, each cell would contain a thin thread of
DNA about 3 meters long.
Purpose: To release (extract) and collect DNA from your cheek cells.
There are two to three basic steps in DNA extraction:
1. Release the DNA
In order to release the DNA the cell must be lysed (broken open) to release the
nucleus and then the nucleus must be lysed to release the DNA.
To lyse the cell and the nucleus, the lipids that make up the membranes must be
broken down. This is done using detergent.
2. Protect the DNA from Enzymes
DNAase enzymes are also released when the cell membrane is lysed. The DNA must
be protected from these enzymes because they will degrade it.
The enzymes can be denatured by heating, using a basic pH or using salt.
3. Precipitate the DNA
In water, DNA is soluble (it is dissolved in the water) and you can not see it.
To precipitate the DNA isopropyl alcohol is used. In isopropyl alcohol, DNA uncoils
and precipitates leaving behind the other cell components that are not soluble in
1. Use a toothpick to scrape inside of both cheeks. Dispose of the toothpick when
finished. BE CAREFUL NOT TO HURT THE INSIDE OF YOUR CHEEK.
2. Wash your mouth with 2 ml of distilled water.
3. Spit water into paper cup.
4. Pour water from cup into test tube.
5. Add 1 ml of extraction buffer:
Extraction buffer recipe
- 200 ml of distilled water
- 1 tsp of salt
- 1 tsp of dishwashing liquid
6. Shake the test tube until suds form.
7. Using a pipette slowly add 1 ml of ice-cold isopropyl alcohol.
8. Wait approximately 3 minutes for the DNA to precipitate.
In paragraph format address the following:
• Describe the steps followed that allowed you to extract DNA from your cheek
• Describe the appearance and solubility of DNA
• How might you have changed the procedure to increase the amount of DNA you