Extracting DNA from Strawberries

INTRODUCTION

DNA or deoxyribonucleic acid, is required in everything living. In this experiment, we will be extracting DNA from strawberries. In order to do this, we will be smashing strawberries and mixing them with an extraction solution. The way that the DNA is able to escape from the strawberry is because the detergent in our extraction liquid, causes the cell to pop open, releasing it into the liquid solution. Not only will the detergent in the extraction liquid cause the cell to pop open, but the salt in the extraction liquid causes the DNA to clump together once released. After the DNA is extracted, the addition of alcohol, will cause the DNA to precipitate, or rise, from the strawberry liquid. Finally taking a thin rod, you can remove the strawberry DNA from the alcohol and examine it closely.

This experiment should be preformed in a lab with adult supervision, or at home in the kitchen with adult supervision.

GENERAL WARNINGS, CAUTIONS, AND DANGERS

  • This experiment is not edible.
  • Wear gloves, goggles, and an apron to protect clothes.

EQUIPMENT

  • Measuring Cup (1/2 cup, 1/3 cup, 1/4 cup, 1 cup)
  • Measuring Spoons (1/2 teaspoon, 1 tablespoon)
  • Glass or small bowl
  • Cheesecloth
  • Funnel
  • Tall Drinking Glass
  • Re-sealable plastic bag
  • Test tube or small glass
  • Thin rod (ex: bamboo skewer or toothpick if the test tube or small glass is not taller than the toothpick)

SUPPLIES

  • ½ Cup 70% Isopropyl Rubbing Alcohol
  • ½ teaspoon Salt
  • 1/3 cup Water
  • 1 tablespoon Dishwashing liquid (ex: Dawn)
  • Strawberries (3)

PROCEDURE

  1. Put the rubbing alcohol in the freezer to chill.
  2. Add ½ teaspoon of salt, 1/3 cup of water, and 1 tablespoon of dishwashing liquid in a glass or small bowl. Mix with a spoon or glass rod.
  3. Set this mixture aside. This is the extraction liquid.
  4. Line the inside of the funnel with the cheesecloth.
  5. Put the stem of the lined funnel into a tall glass.
  6. Remove the green stems from 3 strawberries.
  7. Put the strawberries in a plastic, resealable bag.
  • Make sure all the air is out of the bag and seal it tightly.
  1. With your finger, squeeze and smash the strawberries for 2 minutes.
  2. Add 3 tablespoons of the extraction liquid (step 2) to the smashed strawberries in the bag.
  • Make sure all the air is out of the bag and seal it tightly.
  1. Squeeze the strawberry mixture with your fingers for 1 minute.
  2. Pour the mixture from the bag into the lined funnel (step 5).
  • Let the liquid drip into the glass until there is very little liquid left in the funnel.
  • This might take time, be patient.
  1. After the mixture has been filtered, pour the liquid into a test tube or small glass jar so it is ¼ full.
  2. Take the chilled rubbing alcohol out of the freezer and measure ¼ cup.
  3. Tilt the test tube or small glass jar from step 12 and slowly pour the ¼ cup of cold rubbing alcohol down the side.
  • The alcohol should form a layer on top of the strawberry liquid.
  • Do not let the alcohol and strawberry liquid mix.
  1. The DNA will precipitate into the alcohol layer.
  • The DNA will appear as a gooey clear/white string.
  1. To extract the DNA from the solution, dip a thin rod into the test tube where the alcohol meets the strawberry layer and pull the rod up.

DISPOSAL:

All sold waste can be thrown in the trash and all liquid waste can be washing down the drain with water.

Helpful Video:

Sources:

Science Buddies. “Strawberry DNA.” Science Buddies, Science Buddies, n.d., www.sciencebuddies.org/science-fair-projects/project-ideas/BioChem_p015/biotechnology-techniques/strawberry-dna.

A Recipe for Extracting Raw DNA, www.popularmechanics.com/science/health/a12884/a-recipe-for-extracting-raw-dna-15159362/. Accessed 11 May 2024.