In this lab, you extract and isolate DNA from strawberries using simple, household ingredients.
You’ve probably learned or heard about DNA, but have you ever seen it? With the Strawberry DNA experiment, you’ll extract, isolate, and observe the DNA of a strawberry in a matter of minutes. It sounds impossible, but thanks to special characteristics of strawberries, it’s actually very possible… and simple. You don’t have to be a geneticist and you don’t need an electron microscope. It’s easy, fun, and all you need are some household materials.
Put a bottle of isopropyl alcohol in a freezer. We’ll come back to it later. Measure 6T (90 ml) of water into a small glass container.
Add 2 tsp (10 ml) dish soap to the water.
Stir in a ¼-tsp salt and mix until the salt dissolves. This is the extraction mixture.
Place one strawberry into a plastic zipper-lock bag.
Pour the extraction mixture into the bag with the strawberry.
Remove as much air from the bag as possible and seal it closed.
Use your hands and fingers to mash, smash, and moosh the strawberry inside of the bag. You don’t want any large pieces remaining.
Pour the resulting strawberry pulp and extraction mixture through a strainer and into a medium glass bowl or similar container.
Use a spoon to press the mashed bits of strawberry against the strainer forcing even more of the mixture into the container. From the container it’s in now, pour the extraction mixture into a smaller glass container that holds ¼- to ½-cup (50-100 ml) of fluid. This will help to isolate the DNA on the surface of the mixture.
Add 1 tsp (5 ml) of the chilled isopropyl alcohol to the solution and hold the mixture at eye level. You’re looking for a separation of material that shows up as a white layer on top. That’s the DNA of the strawberry!
Use the tweezers to gently remove the DNA from the solution and lay it on a dish to examine.
HOW DOES IT WORK
Whoa! The long thick fibers you pull out of the extraction mixture are real strands of strawberry DNA. As you may know, DNA is present in every cell of all plants and animals and determines all genetic traits of the individual organism.
While other fruits are soft and just as easy to pulverize, strawberries are the perfect choice for a DNA extraction lab for two very good reasons: (1) they yield way more DNA than other fruits, and (2) they are octoploid, meaning that they have eight copies of each type of DNA chromosome. (Human cells are generally diploid, meaning two sets of chromosomes.) These special circumstances make strawberry DNA both easy to extract and to see.
To extract the DNA, each component of the extraction mixture plays a part. Soap helps to dissolve cell membranes. Salt is added to release the DNA strands by breaking up protein chains that hold nucleic acids together. Finally, DNA is not soluble in isopropyl alcohol, especially when the alcohol is ice cold.
After you select the video you like to watch, you’ll be redirected to a new scene. There, you’ll have everything you need to teach the topic: video, discussion questions, reading material, DIY activity guide, lesson plan, teacher’s guide, and assessment (quiz).
SNOWSTORM IN A JAR (scroll down for written directions or follow the video above)
Glitter (optional, just pretty to watch swirl around)
RAIN CLOUD IN A JAR (scroll down for written directions or follow the video above)
A jar (we recommend a wide mouth shallow one)
Blue liquid watercolors (you can also use water with food coloring just as easily! You can also experiment with different colors and create a rainbow cloud and rain! How pretty would that be?)
TORNADO IN A JAR (scroll down for written directions or follow the video above)
SNOWSTORM IN A JAR
Step 1. Add your baby oil to the jar about 3/4 full.
Step 2. Mix white paint with a bit of water. To be honest we didn’t exactly measure this, it was a few squirts of white pain with about 1/4 – 1/2 cups of water. The exact measurements don’t matter much here as you just want to have a thin water/paint mixture. This is a great time to test out a hypothesis – what happens if you add equal parts paint/water or more paint to water ratio?
Step 3. Add your white paint to the baby oil.
Step 4. Add glitter for some fun visual effects (optional).
Step 5. Drop your Alka-Seltzer tablet one at a time in the jar. Watch as the white paint/water mixture bubbles up from the effervescent effects of the Alka-Seltzer.
RAIN CLOUD IN A JAR
Step 1. Add water to your jar leaving room at the top for shaving cream.
Step 2. Squirt a few big blobs of shaving cream to fill the top of the jar.
Step 3. Add your liquid watercolor in a bowl and suck up a bit with a pipette. Drop the liquid into the shaving cream.
Step 4. Watch and observe the “rain” or liquid watercolor seep down the shaving cream cloud.
TORNADO IN A JAR
Step 1. Pour water into your jar almost to the top.
Step 2. Add a small drop of dish soap. Not too much or else there will be too many bubbles and it will be hard to see the tornado.
Step 3. Add some glitter (optional but cool to see it swirl).
Step 4. Cap your jar and make sure it’s tight!
Step 5. Shake your jar vigorously. First we shook it up and down, then side to side. Set the jar down and watch closely for the tornado forming in the jar!
(10/2/20 update from Homeschooling-Mommo: We had to alter elements to achieve the desired results. 2 drops of dish soap and shake it up in a circular motion – not up/down, side-to-side. Don’t use a lot of glitter or you won’t see the funnel.)