Extracting DNA From Strawberries Experiment

 

 

Extracting DNA from strawberries, or anything, sounds like a complicated procedure performed by people in white lab coats in sterile environments using pipettes and special chemicals. And sure, it can be done that way. Or, you could do it in your kitchen.

I have to admit. Even though I was a biology major and worked as a biologist and researcher, not every area of science excites me. Genetics was such an area for so long. I still despise punnet squares…..

Then one day in a college lab class, we extracted DNA from peas and collected enough to wind it around a glass rod.

I.was.amazed.

This opaque white stringy goo was DNA. No way!

Up until then, DNA was just punnet squares. linked traits, and ways to identify criminals on TV shows. But, NOW I could see it. That made all the difference.

Extracting DNA In Your Kitchen

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.

I have done this experiment many times in labs and with my kids using both peas and strawberries. We usually do this at home with strawberries. because we always have them on hand. We don’t really care for peas.

Try this with your kids and I promise they will be amazed, too!

Supplies

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 (custard cups work well)
• laundry detergent (liquid or powdered)
• ice cubes
• 2 big bowls
• a timer
• salt
• ice-cold rubbing alcohol

Procedure

Before beginning, place the alcohol in the freezer. It will need to be cold to precipitate the DNA.

 

Cut the strawberries into small pieces and put them in a pyrex cup. Mash the strawberries with a fork until the chunks are gone.

Add a tsp of liquid detergent to 1/2 cup warm tap water. Stir. Then, stir into the mashed strawberries.

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.

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.

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.

The strands of DNA can be collected on a plastic fork, toothpick or skewer. Try this extracting DNA 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.

To Learn More About DNA

• Practical ways to show how DNA expresses itself in our bodies 
• Eye color genetics lab
• Peas In A Pod activity and lesson
• DNA And Genetics