Extract DNA from a Strawberry

What it does

In order to study DNA, scientists have to extract it from cells. There are many DNA extraction kits available for scientists to use in the lab, but they all work in roughly the same way. This experiment lets you make your own DNA extraction kit from common household materials. You will extract DNA from strawberries and see the clumps of DNA strands.

What you need

  • Rubbing alcohol
  • Small bowl
  • 1/2 teaspoon salt
  • 1/3 cup water
  • 1 Tablespoon dishwashing detergent (such as Dawn)
  • 3 strawberries (green tops removed)
  • Small plastic zip-top bag
  • Funnel Cheesecloth (or a coffee filter)
  • Tall drinking glass
  • Test tube or small clear glass jar
  • Bamboo skewer (optional)

What to do

  1. Put the rubbing alcohol in the freezer to chill it while you prepare the rest of the experiment.
  2. Mix the salt, water and detergent in a small bowl. This will be your extraction liquid.
  3. Put the strawberries in the plastic bag and squeeze out all the extra air before sealing tightly.
  4. Mash the strawberries with your hands for about 2 minutes until they are mushy.
  5. Add 3 tablespoons of the extraction liquid to the strawberries in the bag. Squeeze out the air and seal the bag again.
  6. Mash the strawberry mixture with your hands for another minute.
  7. Place a layer of cheesecloth inside the funnel and set the funnel on top of the tall drinking glass (so that it will empty into the glass).
  8. Pour the strawberry mixture from the bag into the funnel. Let it drop through the cheesecloth until there is no liquid left.
  9. Throw away the cheesecloth and the strawberry pulp inside it.
  10. Pour the contents of the glass into the test tube or small jar until it is 1/4 full.
  11. Tilt the test tube or jar and very slowly pour rubbing alcohol down the side. The alcohol will form a layer on top of the strawberry juice. Do not let the alcohol mix with the strawberry juice!
  12. Let the contents sit for a few minutes. You should see stringy, whitish stuff collecting between the two layers of liquid. This is DNA! You can gently pull the DNA out with the bamboo skewer if you want.

What it's all about

The detergent you used caused the cells to pop open, or “lyse.” This releases the DNA into the solution. The alcohol causes the DNA to precipitate out of the solution.

Strawberries are easy to use in this experiment because they are easy to mash and they contain a lot of DNA in each cell. However, you can do this experiment on most any living (or formerly living) thing. Try this experiment using other fruits and vegetables or soft meats (like chicken liver).