Science Smarts: Extracting fruit DNA!

By PATTY ROOKS on January 28, 2023.

I can hardly believe it’s that time of year – Operation Minerva time! Operation Minerva is a long-standing tradition and one of the first programs to ever be hosted by Praxis. It is a one day conference for girls in Grade 9 f rom southeastern Alberta.

We are hoping that by showcasing local women in STEM careers, more of our students will return to the wonderful communities in southeastern Alberta with amazing STEM careers which will allow our communities (especially the rural ones) to continue to thrive!

I know there is not room for all of the girls in southeastern Alberta to attend, so I thought I would share one of my favourite workshop activities with all of you. Let’s get started!

Remember to ask an adult before doing this experiment.

Materials

Safety goggles

Ice

Water

Measuring spoons

Measuring cups

Plastic zipper bag (large AND small size)

Sodium chloride (salt)

Rubbing alcohol (preferably 99%)

Wooden toothpick

Two bowls

Liquid soap/shampoo

Two CLEAR plastic cup

Strawberries/banana

Fork

Paper towel

Scissors

Procedure

1. Put your safety goggles on.

2. Make an ice bath with one of the bowls, some water and the rubbing alcohol. Set the bottle of rubbing alcohol in here and allow it to chill.

3. Place about six strawberries or half a banana in one of the bowls and mash it up REALLY well with the fork.

4. Measure 125 mL (1/2 cup) of WARM water and add 5 mL (one teaspoon) of liquid soap to the water.

5. Add the smashed up fruit to this mixture and stir it well.

6. Allow mixture to sit for five minutes on the counter.

7. Make another ice bath. Add the fruit /soap mixture and allow it to chill for five minutes.

8. Snip one corner off the plastic bag. Take one of the plastic cups and place the small plastic bag in it. Line the top of the bag with a few paper towels.

9. Carefully pour the mixture over the paper towels and into the plastic bag. Go slowly as you want the mixture to filter through the paper towels.

10. Once the mixture has filtered through the filters you should have a clear liquid in the bottom. Remove the bag and discard.

11. Add 1 mL (1/4 teaspoon) of salt and stir well.

12. Measure how much liquid you have with the measuring cups and pour it back into a clear glass. Add this amount of rubbing alcohol to your mixture now. I like to GENTLY pour it down the side of the clear glass.

13. Allow this to sit for a minute and observe.

14. You should see the mixture separating.

15. Take the wooden toothpick and twist it around in this cloudy mixture.

16. Remove and observe.

17. This is fruit DNA!

What is going on?

I know this was a long experiment but how exciting to be able to see DNA, by breaking down the cell walls in the fruit we mashed it up. In order to separate out these cells, we had to use the detergent. We did not want it to go too far and had to stop this mixture from breaking down any further chilling it in the ice bath. By adding the salt and rubbing alcohol the DNA was allowed to break apart from the rest of the SOLUTION and float for the top for us to easily extract!