Have your kids ever wondered why their hair is one colour, while their friend’s hair is a different colour? Or why dogs are hairy and birds have feathers? It is all coded into the most fundamental blueprints for a living being… our DNA. Today we are doing a kitchen science experiment that allows us to see DNA!
Strawberry DNA Extraction Lab
Kitchen Science Lab for Kids
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Most kids have heard of DNA. If they have been through the dinosaur stage, it seems like DNA is a natural part of learning all about dinosaurs. But did you know you can do a simple kitchen lab and hold DNA in your hands (well tweezers)?
This experiment is an incredible biology lab for students in Upper Elementary through High School.
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What is DNA?
OK, our kids might have heard of DNA but do they really know what it is? Let’s get some terminology and explanations out of the way first.
DNA stands for deoxyribonucleic acid, it is found in the cells of all living organisms and is basically the instructions or blueprints for our bodies. Each cell has an entire copy of these instructions in its nucleus.
Scientists study DNA because it is like the textbook for an organism. DNA is our genetic code. It is packed full of information that controls how an organism looks and functions. When they study DNA they can learn about extinct species (like dinosaurs), they can create vaccines and medications, they can use DNA to solve crimes, and so much more. The study of DNA is used in so many different ways by scientists all over the world.
DNA is a double helix with the two strands chemically linked like a spiral shaped ladder. It lives in a cells nucleus in pairs called chromosomes. Humans have 46 chromosomes arranged in 23 pairs.
DNA was discovered in 1869 by Friedrich Miescher, but Miescher’s discovery was just the beginning. It wasn’t until the 1940’s that scientists started to understand how DNA was involved in hereditary traits. To this day, scientists all over the world are continually working to unlock the secrets hidden the DNA code of our cells.
Why is Strawberry Used for DNA Extraction?
There are some very good reasons why strawberries are the perfect DNA extraction experiment for a student lab.
- Strawberries are easy to access in most places in the world.
- They are easy for kids to pulverize with their hands.
- Strawberries contain enzymes called pectinases and cellulases that help to break down cell walls, this helps release that precious DNA.
- A strawberry is octoploid. That means they have eight copies of each type of DNA chromosome. Human cells are diploid, meaning they have two sets of chromosomes. That means there is a LOT of extra DNA to extract from a strawberry leading to higher success rates for students.
That said, once your students have mastered extracting DNA from strawberries, why not challenge them to see if they can extract the DNA from other fruit? Bananas, kiwis and even oatmeal are great options!
How to Extract DNA from a Strawberry
Now we have talked a lot about DNA and strawberries, let’s get started on our DNA extraction lab.
Supplies and Materials
Ripe strawberries (a little over ripe is even better!) If you use frozen, make sure they are completely thawed.
Sealable plastic bag (thicker freezer bags are best)
Dish soap (we used a clear one so the colour did not affect our visuals, but any will work)
Salt (table salt – NaCl)
Isopropyl alcohol (rubbing alcohol will work too)
Coffee filter or paper towel
Clear cups or test tubes
Tweezers or a chop stick will work
Syringe, measuring cups, measuring spoons (whatever you have on had will work!)
Paper towels (for clean up)
Optional but highly recommended:
DNA Extraction Directions
Place the alcohol in the freezer for at least an hour. You want it cold.
Create the DNA Extraction Liquid. In one cup mix 60mL (1/4 cup) of water (room temperature) with 1 tablespoon of dish detergent soap and 1 teaspoon of salt. Gently mix (you don’t want to form bubbles).
Remove the greens from the strawberries and place two in a plastic bag and seal it tightly. Then start mashing! You want to mash it up completely until there are no lumps. Use your fingers and palms to mash it. Don’t use any tools as that can rip the bag, plus this is more fun for the kids!
Once mashed, add 20mL of the extraction liquid. Mash it around for one more minute.
Add a coffee filter to a clean cup. Press it into the cup so the smashed strawberries can be poured in without overflowing.
Pour the mashed up strawberry mixture into the filter so only the liquid flows into the cup. You can VERY GENTLY lift and squeeze the filter if you need to get a bit more liquid out. Be very careful you don’t rip the filter. You don’t want any solids getting into the glass, only the liquid.
If you find the coffee filter doesn’t work for you, you can try putting the coffee filter in a funnel or use cheesecloth instead of the coffee filter. Cheesecloth will not rip.
Pour about a tablespoon of the cold isopropyl alcohol into the cup. Tip the cup so it slides down the side of the glass.
Watch as the DNA strands separate from the red strawberry liquid!
Use your tweezers or a chop stick to lift out the DNA so you can examine it.
What does Strawberry DNA look like?
Instead of trying to explain it… here is a picture!
Strawberry DNA will look like a stringy white substance since DNA molecules form long chains. As my kids put it, “it looks like snot!”
But if you carefully stretch it out you can see more of the details of those strands of DNA.
We really enjoyed using a magnifying glass. Then we created a slide with our strawberry DNA and looked at it under the microscope. If you are making slides, ensure you stretch it out, both length and width so you can really expose all the details under the microscope.
How does Strawberry DNA Extraction Work?
Everything works together in this science lab to perfectly extract the strawberry DNA. Here is what each item is doing.
Dish soap helps to dissolve the cell membrane, which is a lipid (fatty) layer.
Salt (NaCl Sodium chloride) helps to remove protein chains that bind the DNA. It also helps to keep the proteins in the liquid so they don’t precipitate in the alcohol along with the DNA.
Isopropyl alcohol causes the DNA to precipitate (become solid) because DNA is not soluble in alcohol, especially cold alcohol.
Why Do Strawberry DNA Extraction?
This is such an incredible biology science lab to do with your students. DNA is normally something we can’t see or observe, making it harder for kids to understand and appreciate. With this experiment we give students the chance to work with DNA and make this important part of all life forms a more tangible concept.
This is one incredible experiment students will never forget!
Next on your DNA investigations, build a DNA Model
Interested in doing more Biology labs?
Learn more about cells and cell structure in our Naked Egg Cell Experiment.
Check out our incredible Heart Study including building a model of a beating heart.