Science Smarts: DNA extraction

By Patty Rooks on August 30, 2025.

It is a special someone’s birthday this week, and unfortunately, I will not see them to celebrate, so I am dedicating this week’s article to them … this person readily volunteers at all Praxis events whenever they can, and if they cannot, they work tirelessly behind the scenes prepping everything so we always have a successful event, with a hands-on learning kit ready to go or sorting the NXT out for me in a hurry! In honour of this tireless volunteer, I thought I would share one of their favourite experiments. Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

– Rubbing alcohol

– Access to a freezer

– Strawberries

– Salt

– Water

– Ice cubes

– Liquid dish soap

– Measuring cups

– Measuring spoons

– Mixing bowls (3)

– Spoon

– Wooden skewer sticks

– Cheesecloth

– Tall clear glass

– Safety goggles

Procedure

1. As with any science experiment using “chemicals”, put on your safety goggles.

2. Place the bottle of rubbing alcohol in the freezer as it needs to be VERY cold for this experiment to work.

3. Remove the green stems from three or four strawberries and place them in a mixing bowl. Mash them up REALLY well with the back of a spoon.

4. Measure 125 mL (1/2 cup) of water and add 5 mL (one teaspoon) of liquid soap. Mix well but try not to get too many bubbles going. Be gentle. Pour over the mashed up berries. Stir gently.

5. Fill a separate bowl with warm water. Place the berry mixture (in the bowl) into the warm water. It needs to rest here for about ten minutes or so. Stir often and observe.

6. Take the final mixing bowl and fill it with ice.

7. Remove the strawberry mixture form the warm water and rest it in the bowl of ice.

8. Allow this to sit for about five minutes, stirring often. Make frequent observations!

9. Place a piece of cheesecloth over the mouth of the tall clear glass. Let it “droop” a bit into the glass – you’re creating a filter. You may want to secure it in place with a rubber band.

10. Carefully pour your strawberry mixture into the cheesecloth. Go slow and allow it to filter into the glass.

11. Remove the cheesecloth and add 1 mL (1/4 teaspoon) of salt to mixture and stir well.

12. Take the rubbing alcohol out of the freezer.

13. Take the strawberry mixture, tip the glass slightly and pour a steady stream of the ice cold rubbing alcohol down the side of the glass until it is about doubled in volume.

14. Allow the mixture to sit for a few minutes. Be patient and observe what is happening.

15. Take a wooden skewer and twirl it in the “cloudy” mixture that floats to the top of the glass.

16. What is this?

17. Be sure to dispose of the mixture safely and DO NOT DRINK OR EAT ANYTHING you make in a “science lab” no matter where you are!

What is going on?

The “slime” like substance that you twirled around your wooden skewer is strawberry DNA!! It is hard to believe that this is all the information you need in order to make an identical strawberry plant.

You extracted the DNA in a few steps. When you masked up the strawberries, you actually broke down their cell walls. You further separated the cell walls by adding the detergent. It was important to stop the process of breaking apart the DNA by “chilling” the mixture in the ice bath. The final step in adding the salt and rubbing alcohol further allowed the DNA to break apart and rise to the top of the glass.

Pretty amazing how you can extract something so complicated through such a simple process! Try this experiment with different fruits or vegetables and compare the DNA!

Mark your calendars for the praxis AGM on Wednesday, Sept. 17 at 7 p.m. We are always looking for new board members that want to share their love of science. Contact Praxis for further details.

Patty Rooks, senior scientific consultant Praxis Science Outreach Society. Praxis has moved! We are very fortunate to be located in the Community Futures Entre Corp Building at #202 556 Fourth St. SE, Medicine Hat, Alberta, T1A 0K8. For all your science needs, please email praxis@praxismh.ca.

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