It’s strawberry season! And that means it’s time for Experiment #1 in Yellow Scope’s SUMMER SCIENCE SERIES.
You may have heard of genes and DNA. DNA is found inside the cells of all living things – from humans to guinea pigs, and fungus to strawberries. DNA contains the instructions to make living things.
But have you ever seen DNA? In this experiment, you will extract and isolate DNA from strawberries, using a few household chemicals. In just a matter of minutes, you will actually be able to see strawberry DNA!
So save a couple strawberries from your basket and try this fun, simple, and quick experiment!
NOTE: This experiment is designed for children ages 8-12. But younger kids can also have fun experimenting along side an adult.
WARNING: Rubbing alcohol should only be handled by an adult.
WHAT YOU’LL NEED
- supervising adult
- rubbing alcohol
- small bowl
- measuring cup
- measuring spoons
- liquid dish soap
- small zipper-lock baggie
- small sieve
- small clear glass or jar
- toothpick or bamboo skewer
LET’S GET STARTED!
- Put the rubbing alcohol in the freezer to chill. You'll use it later.
- Make the DNA EXTRACTION SOLUTION in a small bowl by gently mixing together (try to avoid making the mixture too bubbly):
- 1/3 cup water
- 1/2 teaspoon salt
- 1 tablespoon dishwashing liquid
You will have enough extraction solution to repeat the experiment several times – or to do the experiment with a friend!
- Remove the green top from the strawberry. Now put the strawberry in the baggie.
- Add 2 tablespoons DNA extraction solution to the baggie with the strawberry.
- Carefully push the air out of the baggie and seal it tightly.
- Use your fingers to squeeze, smash, and mush the strawberry in the extraction solution until there are no large pieces remaining.
- Place the sieve over the small glass or jar.
- Pour the strawberry mixture from the bag into the sieve.
- Once all the liquid has drained through (you can gently push on the strawberry pulp with the back of a spoon to help it drain), remove the sieve and discard the leftover strawberry material.
- Tilt the glass or jar containing the strawberry liquid, and very slowly pour 1 tablespoon of ice cold rubbing alcohol down the side of the glass. The alcohol should form a layer on top of the strawberry liquid. Be careful not to mix the two layers.
- The DNA will collect at the interface between the two layers (the place where to two layers touch). It will look like stringy, gooey, white strands. Look through the side of the glass to see strands of DNA precipitating out of the strawberry liquid.
HINT: Shine a flashlight through the glass to see the DNA even better.
To collect the DNA, carefully dip the bamboo skewer or toothpick into the alcohol layer and swirl around the interface. Carefully pull out the skewer or toothpick and check it out up close!
WHAT’S GOING ON?
Each part of the DNA extraction solution played an important role in extracting the DNA from the strawberry.
- DISH SOAP: helped dissolve and break open the cell membranes
- SALT: helped to break up proteins that surround the DNA to release the DNA strands
- RUBBING ALCOHOL: DNA is not soluble in the alcohol, so it precipitated out/clumped together
Try the experiment again using different fruits and foods you have in your kitchen – bananas, kiwis, or oats! Do you get more or less DNA from different foods?
Let us know how your experiments went and what you observed! We love getting messages and photos!
Marcie Colledge, PhD
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