Extracting DNA From Strawberries Experiment

21 Jun 2014 Kids Activity
Extracting DNA From Strawberries Experiment

All educators of children need to have a bag of tricks and resources they can draw from when they need something extra fun to keep their students’ attention while still teaching them something. One of my favorite resources is KidScienceApp. It is truly science fun at your fingertips.

I can search for science activities by subject or by ingredients I have on hand. My kids like to look through the experiment list and watch the videos. It gets them excited about doing the experiments themselves.
A super fun experiment we found on KidScienceApp is extracting DNA from strawberries.
DNA is the “blueprint” for all organisms. It can be found in the nucleus of the cell. To get to the DNA, the cell wall needs to be broken down and the DNA needs to be separated from the rest of the cell. Believe it or not, we can do this in the kitchen with household items.

The Experiment

Here’s what you’ll need:
  • 3 strawberries
  • measuring spoons
  • 2 one or two-cup pyrex measuring cups
  • cone-shaped coffee filter
  • plastic zip-lock bag
  • small clear plastic or glass cups
  • laundry detergent (liquid or powdered)
  • ice cubes
  • 2 big bowls
  • a timer
  • salt
  • ice-cold rubbing alcohol
Before beginning, place the alcohol in the freezer. It will need to be cold to precipitate the DNA.
Extracting DNA From Strawberries
Cut the strawberries into small pieces and put them in a pyrex cup. Mash the strawberries with a fork until the chunks are gone.
DNA Extraction
Add a tsp of liquid detergent to 1/2 cup warm tap water. Stir. Then, stir into the mashed strawberries.
strawberry dna experiment 2
Place hot tap water into a large bowl (about 1/3 full) and place the glass containing the mashed strawberry mixture into the water bath to warm for 15 minutes. Next, make an ice bath of water and ice in another bowl (about 1/3 full) and place the glass in the ice bath to cool for 5 minutes.
extracting strawberry dna
After 5 minutes in the ice bath, pour the mixture into a funnel lined with the coffee filter. Catch the flitered liquid with another clear glass container.
When filtering is completed, add 1/4 tsp of salt to the filtered liquid and stir. Now, add the same amount of the cold rubbing alcohol as liquid and wait a few minutes.
strawberry dna experiment
DNA will start to precipitate out of the solution. At first, it will look like white foam and then you will start to see cloudy strands on top of the liquid. This photo is just the beginning stage. The photos with lots of DNA turned out too fuzzy to tell what it was! It’s one of the hazards of doing a super fun experiment with the kids. Photos are an after thought!
The strands of DNA can be collected on a plastic fork, toothpick or skewer. Try this experiment and make sure you touch the strands of DNA. What do they feel like?

What happened?

DNA is located in the nucleus of every living cell. It is the instruction manual for every single cellular process that happens within that organism. While this complex molecule might seem too complicated for us to study without a PhD, the truth is that we can study it in our own kitchen. We can actually separate it from the other parts of the cell so we can see DNA with our own eyes.
First, the cell walls that hold the DNA have to be broken down. The mashing of the strawberries allow us access to all the individual cells of the strawberries. The detergent breaks down the cell membranes by dissolving the lipids (fats) and proteins that make up the membranes. These fats and proteins bind to the detergent and precipitate out of the solution. The warmth of the hot water bath speeds up this reaction and the cold from the ice bath slows the reaction so that the DNA itself is not broken down.
When the mixture is filtered, a solution is collected that contains DNA without the strawberry solids. Since, DNA is soluble in water, alcohol is added to precipitate the DNA. DNA will be drawn into the alcohol layer of the mixture.
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