Cells from the lining of your mouth come loose easily, so you will be able to collect cells containing
your DNA by swishing a liquid around in your mouth.
The cells from the lining of your mouth also come off whenever you chew food. How do you think
your body replaces the cells that come off the lining of your mouth when you eat?
To extract DNA from your cells, you will need to separate the DNA from the other types of biological
molecules in your cells. What are the other main types of large biological molecules in cells?
You will be using the same basic steps that biologists use when they extract DNA
Getting Your Sample of Cells
Obtain a cup with sports drink. You will need to get thousands of your cheek cells in the sports drink
in order to extract enough DNA to see. Therefore you should swish the sports drink around in your
mouth vigorously for at least one minute. Then spit the drink back into the cup.
Step 1: Detergent
Add a small amount of detergent to a test tube (about 0.25 mL). Put a glove on the hand you will use
to hold your test tube, not the hand you will use to pour. Now carefully pour the drink containing your
cheek cells into the test tube with detergent until the tube is half full Dishwashing detergent, like all soaps, breaks up lipids. This is why you use detergents to remove
fats (which are lipids) from dirty dishes. Adding the detergent to you cheek cell solution will break
open the cell membranes and nuclear membranes and release your DNA into the solution.
Step 2: Enzymes
Add a pinch of enzyme (meat tenderizer) to your test tube. With your gloved thumb (or palm)
covering the top of the test tube; gently invert the tube five times to mix. Let the mixture sit for at least
10 minutes. While you are waiting, you will learn about the structure of DNA. Remove your glove
and throw it in the garbage.
Why am I adding enzymes?
The nucleus of each of your cells contains multiple long strands of DNA with all the instructions to
make your entire body. If you stretched out the DNA found in one of your cells, it would be 2-3
meters long. To fit all of this DNA inside a tiny cell nucleus, the DNA is wrapped tightly around
proteins. The enzyme in meat tenderizer is a protease, which is an enzyme that cuts proteins into
small pieces. As this enzyme cuts up the proteins, the DNA will unwind and separate from the
proteins.
The protease in meat tenderizer actually comes from plants, but animals also make proteases.
Where in your body do you think you make protein-cutting enzymes?