DNA Extraction from Wheat Germ

Developed by the Science Museum of Minnesota, Susan Fleming

Supplies:

• wheat germ
• distilled water
• liquid hand soap
• meat tenderizer
• baking soda
• plastic cup
• alcohol (either 70% isopropanol or 95% denatured alcohol)
• measuring spoons
• mixing spoon
• glass stirring rod
• plastic dropper
• 100 ml graduated cylinder
• 15 ml plastic tube

Procedure:

1. Using the graduated cylinder, measure out 100 mls of water and pour into the plastic cup.
2. Add 1 tablespoon of wheat germ to the water and mix.
3. Add one pump of liquid soap, stir for 1 minute.
   
   You will notice that the mixture will get very thick. This is because the cell membranes are broken apart by the soap, releasing nucleic acids, proteins and other components. The DNA makes the solution very viscous.
   
   
4. Add 1/2 teaspoon of meat tenderizer and 1 teaspoon of baking soda. Stir to mix.
   
   The meat tenderizer chews up the proteins which hold the DNA tightly coiled inside the cell and destroys the enzymes which break DNA into small pieces. We want the DNA to be long, stringy strands, so it will wrap around the glass rod. The baking soda acts as a buffer system and brings the pH up to 8.0. This helps proteins separate from DNA.
   
   
5. Stir for 1 minute. Allow the wheat germ to settle to the bottom; almost all the wheat germ should be on the bottom of the cup. This should take about 2-3 minutes.
6. Once the wheat germ has settled, use the plastic dropper bulb and transfer two or three droppers full of the wheat germ liquid at the top of the cup to a tube. Some of the wheat germ solid may transfer over to the cup; that is okay, but you don't want all the wheat germ to contaminate your solution.
7. Using the squeeze bottle containing alcohol dribble alcohol down the side of the tube. Add an amount of alcohol equal to the wheat germ liquid.
   
   Try not to mix the two layers. Let the tube sit for a minute or two, you will see large and small bubbles appear at the interface between the two layers. This is the DNA, it is insoluble in alcohol.
   
   
8. Carefully swirl a glass stirring rod at the interface of the two layers using small circles to spool or wrap the DNA around the rod. If you keep swirling and are careful not to mix the two layers, you will be able to pull out a big wad of DNA.

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