Kids, would you like to see DNA extracted from your very own mouth? Deoxyribonucleic acid, or DNA, is present in all living things from bacteria to plants to animals. In animals, it is found in almost all cell types: muscles, reproductive cells, hair roots, and skin cells -- anything that has a nucleus. The basic procedure for extracting DNA in a laboratory is:
· Collect cells.
· Split cells open and release contents (proteins, fats and carbohydrates).
· Destroy enzymes which break apart DNA.
· Separate DNA from other cell components (proteins, fats and carbohydrates).
· Precipitate DNA.
· Resuspend DNA in solution so it can be studied.
Please note: All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.
Many of these steps can be accomplished in a simple experiment at home. You will need a bottle of clear Gatorade™, Dixie™ cups, dishwashing liquid, rubbing alcohol and a clear vial with a screwcap (20 ml is a good size).
First, chill the bottle of rubbing alcohol on ice. Pour a small squirt of dishwashing liquid into the vial and add water (1 part detergent to 3 parts water). Put 15-20 ml of Gatorade™ in your mouth and swish it around for 30 seconds, gently grinding the inside of your cheeks against your teeth. Spit this into a clean Dixie™ cup. Pour this into the vial of detergent until nearly full. Gently rock the vial back and forth for a few minutes. Do not agitate – you don’t want to make foam or bubbles. Now add a teaspoon of the chilled rubbing alcohol to the vial and let sit for a few minutes. You should see the DNA separate out as white strands.
What’s happening? The salt solution keeps the cells from lysing, or splitting open, too soon. The detergent releases DNA from the nucleus by breaking open the fatty molecules the make up the cell membranes and helps remove proteins associated with DNA. DNA doesn’t dissolve in rubbing alcohol, so it precipitates out as white strands. If you took all of the DNA from a single cell and laid it end to end, it would be almost 2 meters long!
TIPS: A 0.9% saline solution will also work (9 gm NaCl in 1 liter distilled water) but Gatorade™ tastes better; clear is best but if you can’t find it then the yellow lemon-lime should work. Powerade™ doesn’t have enough salt to work.
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Kathleen Carrado Gregar, PhD, Argonne National Labs
[email protected]
February 2011
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References:
Elizabeth Neis and also the California Science Center at:
http://www.californiasciencecenter.org
The exact reference:
http://www.californiasciencecenter.org/Education/GroupPrograms/HomeSchool/docs/DNA.pdf
