DNA Extraction
Extract DNA with household materials and see it with your own eyes!
Materials
- Kiwi (OR 2 strawberries OR half a frozen banana)
- Table salt
- Bottled water
- Clear cup
- Spoon or straw
- Tape or elastic band
- Liquid dish detergent
- Cheesecloth (3 layers)
- Cold isopropanol (purchase at pharmacy, place in the fridge to cool)
- Wooden or glass stir stick
Preparation
Make the buffer solution by mixing 1 teaspoon of table salt in 100 mL water
Make the soap solution by mixing 3 mL (3/4 teaspoon) liquid soap with 27 mL (2 tablespoons) water
The salt solution will help precipitate proteins and carbohydrates away from the DNA
Step 1
Scoop out the kiwi flesh into a resealable bag and mash for 2 minutes
Mashing helps to break apart the cells and loosen the tough cell wall
Step 2
Add 10 mL of buffer solution and grind for at least 5 minutes. Use your weight and strength to really mash it up!
Step 3
Assemble the filter by covering the top of a cup with the three layers of cheese cloth.
Tape (or use an elastic band) the cheese cloth around the cup.
Step 4
Pour the kiwi mash through the filter. Let the solution drip into the cup.
Tip: You can get extra juice by squeezing the kiwi through the cloth.
Step 5
Add 3 mL of the soap solution to the filtered liquid.
Swirl gently to mix.
The soap will help break open the cellular and nuclear membrane to release the DNA
Step 6
Pour 2 volumes* of the cold isopropanol down the length of a straw (or the back of a spoon) into the kiwi liquid.
The isopropanol needs to form a layer on top of the kiwi liquid.
*Two volumes = twice the amount of kiwi liquid
Step 7
Let the liquid sit. The DNA should precipitate where the kiwi liquid meets the alcohol. You can use the stir stick to spool some out of the cup!
DNA dissolves in water but precipitates in alcohol!
Notes:
The above activity is fun for all ages.
It is particularly useful in grades 9, 10, 11, and 12 to introduce various discussions about DNA.
