Scientists generally use special materials to extract DNA from cells. A DNA extraction normally requires the addition of a protease enzyme, which breaks down other parts of the cell nucleus to free the DNA. However, kiwi fruit naturally contain protease enzymes, according to St. John's School. This makes extracting kiwi DNA a procedure simple enough to perform in your school laboratory, or even in your own kitchen. The extraction solution contains detergent, which breaks down cell membranes; and salt, which causes the DNA to clump together, according to Iowa State University.
- Skill level:
Things you need
- 250ml or 1 cup container
- 90ml or 6 tbsp water, preferably distilled water
- 2g or 1/4 tsp salt
- 10ml or 2 tsp clear shampoo or liquid detergent
- 2 or 3 kiwi
- 1000ml or 4 cup container
- 2 saucepans or other large shallow containers
- 500ml or 2 cup container
- Funnel or strainer
- Coffee filter
- Test tube
- 2 pipettes, or a measuring spoon and a medicine dropper
- 10ml or 2 tsp cold ethanol
- Test tube rack
- Wire hook or glass rod
Add the salt and the 90ml of water to the 250ml container. Stir to dissolve the salt.
Add the shampoo or detergent to the salt solution. Stir gently so the soap does not foam. This creates your extraction solution.
Peel the kiwis and chop them into small pieces -- about 12 pieces per kiwi.
Put the kiwi in the 1000ml container and mash it with a fork.
Pour the extraction solution into the container with the kiwi.
Prepare a hot water bath by putting about 3 inches of water into a heat-resistant container large enough to hold the container with the kiwi mixture. Heat the water to about 60 degrees C.
Place the container holding the kiwi mixture into the hot water bath. Incubate for 10 to 12 minutes -- don't leave it there for longer than 15 minutes. Monitor the water temperature with the thermometer to ensure it remains between 50 and 60 degrees C.
Prepare an ice bath while the kiwi mixture is incubating. Put several ice cubes into a shallow container, then add water until it reaches about 3 inches deep.
Move the container with the kiwi mixture from the hot water bath to the ice bath. Leave it there for 5 minutes, stirring occasionally.
Place the funnel or strainer over the opening of the 500ml container while the kiwi mixture is cooling. Place the coffee filter inside the funnel or strainer.
Pour the kiwi mixture into the funnel and allow the liquid portion to filter into the container beneath. It may take more than an hour for all the liquid to filter through, but you can recover an adequate amount for the experiment in about 5 minutes.
Transfer 5ml or 1 teaspoon of the liquid to a test tube using a sterile pipette or a clean measuring spoon.
Add 10ml or 2 teaspoons of cold ethanol to the test tube. Use a pipette or medicine dropper to add the ethanol slowly so it does not mix with the liquid.
Set the test tube in a test tube rack and let it sit for 2 to 3 minutes. You should see a white substance form in the layer of ethanol -- this is the kiwi DNA.
Remove the DNA from the solution using a wire hook or glass rod.
Tips and warnings
- Place the bottle of ethanol in a freezer before beginning the experiment to get it as cold as possible. Ethanol will not freeze solid in the freezer because it has a very low freezing point of -114 degrees C.
- Make sure all your containers and utensils are very clean before you begin the experiment, so that the kiwi mixture is not contaminated.
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