In this experiment you will be able to isolate Deoxyribonucleic Acid (DNA) from onion cells using a simple extraction procedure. The procedure will take approximately 10-15 minutes and will involve several stirring and filtering steps. At the end of the procedure you will be able to spool the long, sticky, stringy DNA strands out of solution.
- onion, chopped
- meat tenderizer
- liquid soap
- tea strainer
- glass rod
- 70% isopropanol
- plastic cups
- Dissolve 1 teaspoon each of salt and meat tenderizer into 50 mls (1/4 cup) of warm water. Stir until the salt is dissolved.
- Place the chopped onion and salt solution into the blender. Turn blender on briefly to homogenize the onion. The solution should be lumpy.
- Gently mix the onion and water from the blender with a squirt of liquid soap in a plastic cup. Mix for about five minutes. The soap contains molecules that break open the onion cells and allow the DNA to leak out.
- After 5 minutes, filter some of the soapy onion mixture through a strainer into another plastic cup.
- Add an equal volume of 70% isopropanol to the total amount of liquid in the plastic cup. The alcohol is less dense than the DNA solution and will float on top. Small bubbles may adhere to the DNA strands.
- At the alcohol/water interface the DNA will precipitate as a milky white substance. You can do one of two things:
- Carefully mix the alcohol and water together to see the DNA clump into a white mass.
- Using a glass rod the DNA can be "spooled." Carefully insert the glass rod into the cup just below the alcohol/water interface. Swirl the rod and observe the long sticky DNA molecules collect onto the rod.
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