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.
Raffia (ribbon used for hair, found in craft stores)
Cardstock or Cardboard
Hot Glue Gun & Glue
1. Start off by using Elmer’s glue to glue on your craft sticks, 7 of them, to your cardstock or cardboard.
It really doesn’t matter what you use for the backing just as long as it is strong enough to support the sticks. Also, make sure that you cut your backing so that it’s no longer or wider than the popsicle sticks. Let dry!
2. This is the step the parent will want to help with. Hot glue a few strands of the raffia onto one craft stick for the scarecrow’s hair.
I just cut a few pieces for each side. Once the hot glue is dry you can then glue the stick onto the rest of the scarecrow body.
3. We choose to paint the scarecrow at this point. If you think it would be easier for your kids to paint prior to attaching the hairpiece then you can do that beforehand. We just found it easier to paint afterward.
Now that everything is painted you get to sit and watch paint dry. Luckily it’s just craft paint and it will be dry in minutes, not hours.
4. The next step is to paint on the adorable face. Depending on the age and painting skill level of your children you could always paint the face on for them or cut out pieces of felt or foam and attach with glue.
We didn’t add anything to the hat but you could also add a flower and turn this into a scarecrow girl. Just dress it up, however, you like it.
5. Attach magnets to the back of your scarecrow. We used two .75 inch adhesive magnets to hold ours up. That’s it, you are all done with your popsicle stick scarecrow.
To make this fun spiderweb craft, you will need construction paper or tag board. We used black paper because it provides a nice “pop” from the paint colors. But any color, or even white paper, will work. You’ll also need a pencil to draw with, Elmer’s glue, table salt, watercolor paints, and a soft brush.
Start by drawing a dot with a pencil for the center of the spider web. Draw lines freehand or with a ruler that intersect the center point and go from one edge of the paper to the other. It is better to err on the side of fewer lines rather than too many as the glue will make the lines thicker.
Use your pencil to draw curved lines between each “ray” of the spiderweb. Again, encourage kids to make these line farther apart than they might if they weren’t being traced with glue.
TRACE YOUR SPIDERWEB WITH GLUE
Trace each long ray of the spider web with glue then move on to the curved lines that connect the rays. The lines will be the smoothest if the lid of the glue bottle doesn’t touch the paper. You could even do a practice run in which kids get to make a drizzled free form design before they move onto their spiderweb.
ADD SOME TEXTURE TO THE SPIDERWEB
While the glue it still wet give each child a ramekin of table salt. Use two fingers to pinch the salt and sprinkle it on top of the wet glue. Cover the glue with salt completely and gently slide off the extra.
The spiderweb will need to dry before moving onto the next step. Dry time is usually overnight but depends on humidity levels as well as the thickness of the glue lines.
PAINT YOUR SPIDERWEB
When your spiderweb is dry it’s time to add some color. Using a soft brush, plenty of water, and watercolor paints add a drop or two of color to a salt line. Drop and dab the paint. No scrubbing or the salt and glue will melt away, dissolving your spider web. A light touch is crucial!
Watch the color spread down the line of glue and salt. Even on dark paper the color is vibrant and has a “pop.” Encourage kids to use different colors next to one another and watch as they overlap and blend together.