How to Extract DNA from a Strawberry

Have you ever wondered how scientists get a sample of DNA from a plant, animal, or other organism? All living organisms have DNA. DNA, which is short for deoxyribonucleic acid, is the blueprint for almost everything that happens inside the cells of an organism — overall, it tells the organism how to develop and function. DNA is so important that it can be found in nearly every cell of a living organism. In this activity, you will make your own DNA extraction kit from household chemicals and use it to extract DNA from strawberries. (in 20-30min!)

Materials

• Rubbing alcohol

• Salt

• Water

• Strawberries (3)

• Dishwashing liquid for hand-washing dishes

• Measuring cup for liquids

• Measuring spoons

• Glass or small bowl

• Funnel

• Tall drinking glass

• Cheesecloth

• Re-sealable plastic sandwich bag

• Small glass jar, e.g., spice jar or baby food jar

• Bamboo skewer, available at most grocery stores. If you are using a baby food jar or a short spice jar as your small glass jar, you could use a toothpick instead of a skewer.

Prep Work

1. Chill the rubbing alcohol in the freezer. You will need it to be very cold to do the activity.

Instructions

1. Mix 1/3 cup (C) water, ½ teaspoon salt, and 1 tablespoon (tbsp.) dishwashing liquid in a glass or small bowl. Set the mixture aside for now. This is your extraction liquid, which is what you will use to extract (or remove) the DNA from the strawberries.

2. Completely line the funnel with cheesecloth. Put the funnel's tube into a tall drinking glass (not the glass with the extraction liquid in it). Set this setup aside for now.

3. Remove the green tops from the strawberries and discard the tops. Put the strawberries in a re-sealable plastic sandwich bag and push out all of the extra air. Seal the bag tightly.

4. With your fingers, squeeze and smash the strawberries for two minutes. How do the smashed strawberries look?

5.  Add 3 tbsp. of the extraction liquid you prepared to the strawberries in the bag. Push out all of the extra air and reseal the bag.

6. Squeeze the strawberry mixture with your fingers for one minute. How do the smashed strawberries look now?

7. Pour the strawberry mixture from the bag into the funnel. Let it drip through the cheesecloth and into the tall glass until there is very little liquid left in the funnel (only wet pulp remains). How does the filtered strawberry liquid look?

8. Pour the filtered strawberry liquid from the tall glass into the small glass jar so that the jar is ¼ full.

9. Measure out ½ C of cold rubbing alcohol. Tilt the jar and very slowly pour the cold rubbing alcohol down the side of the jar. Pour until the alcohol has formed approximately a one-inch deep layer on top of the strawberry liquid. You may not need all of the ½ cup of alcohol to form the one-inch layer. Do not let the strawberry liquid and alcohol mix.

10. Study the mixture inside of the jar. The strawberry DNA will appear as gooey clear/white stringy stuff.

11. Dip the bamboo skewer into the jar where the strawberry liquid and alcohol layers meet and then pull up the skewer.

Did you see anything stick to the skewer that might be DNA? Can you spool any DNA onto the skewer?