Tuesday, May 24, 2011

Strawberry DNA Extraction

Adapted from Arizona State University’s Chain Reaction Extract DNA from a Strawberry activity found at: http://chainreactionkids.org/activities-extract-dna-from-a-strawberry

It's a great time of year in NC, because for a few weeks now it's been Strawberry season! Strawberries top my list of favorite fruits so I often get overzealous when buying them and end up having to pick out some overripe berries. What to do with those berries? If you're a 4-H leader, a 4-Her, the parent of a curious kid in need of entertainment, a kid at heart, or any combination of the above you should try this strawberry DNA extraction experiment!

Supplies

  • Rubbing Alcohol (2 teaspoons or slightly more per extraction)
  • Small bowl
  • Extraction liquid (enough for a couple batches of strawberries):
    • 1/2 teaspoon salt
    • 1/3 cup water
    • 1 Tablespoon dishwashing detergent (e.g. Dawn)
  • 3 strawberries (with green tops removed)
  • Small plastic zip-top bag
  • Funnel
  • Cheesecloth or coffee filter
  • Tall cup (tall enough to put the funnel in without the funnel tip reaching the bottom)
  • Dropper or spoon for liquid transfer between containers
  • Test tube or small clear glass jar/canister
  • Bamboo skewer or toothpick depending on the size of your test tube or glass jar used for extraction (see directions for details)

Procedure

  1. Put the Rubbing Alcohol in the freezer. It will chill while you complete the first phase of the experiment.
  2. Combine the ingredients for the extraction liquid (salt, water, and detergent) in a small bowl. Set aside.
  3. After removing the green tops from the strawberries place them in a small plastic zip-top bag, press any extra air out and then seal the bag.
  4. Mash the strawberries up until all of the contents are squished (around 2 minutes). Set aside.
  5. Put the funnel in the cup and place the cheesecloth or coffee filter inside the funnel to prevent the strawberry chunks from getting into the glass.
  6. Take your bag of strawberry mush and, pushing the contents away from one of the bottom corners, cut that corner off and push the contents out onto the cheesecloth or coffee filter and allow the liquid to flow into the cup for a few minutes.
  7. Remove the cheesecloth or coffee filter and all of the strawberry pulp inside it and throw them away.
  8. Pour the contents of the cup (strawberry liquid) into the clear jar or test tube until the container is about ¼ of the way full.
  9. Remove the rubbing alcohol from the freezer.
  10. While tilting the jar or test tube use a dropper or spoon to gently pour the rubbing alcohol down the side of the jar or test tube taking care that the strawberry liquid and rubbing alcohol don’t mix.
  11. Allow the contents to sit for a few minutes and you will begin to see some white cloudy material collecting between the two layers of liquid. This is DNA!
  12. Once you see the DNA you can use the bamboo skewer or toothpick to remove some pieces of the DNA for a closer look.

Follow Up Information and Questions

So how did this work? Well, the extraction liquid you created by mixing the water, detergent, and salt caused the strawberry cells to lsye or split open and spill out their contents including their DNA. Then the addition of the alcohol caused this DNA to precipitate out of the strawberry liquid.

Now that you know how to extract DNA using common household items why don’t you try it with some other fruit? What other fruit would you choose? Why? Do you think another type of fruit will work as well as strawberries did?

Happy experimenting! Let us know what you thought and what other fruit you tried in the comments!


1 comment:

  1. can you do dna with different fruits

    ReplyDelete