In the Robot Test Kitchen, we talk about five main barriers that we typically face in conducting technology programming in our libraries: time, budget, skill, interest, and support. It’s our belief that most of these are not impossible barriers, but sometimes it’s hard to see how. Especially when things like your time and budget are already stretched paper thin.

On Tuesdays, we’re tackling the budget question with programs you can run at your library for under $10. We’re also addressing the interest and support questions by asking you to share your inexpensive STEM programs in the comments, and to let us know what kinds of feedback you’ve gotten when you’ve tried these or similar programs in your buildings! This week: Strawberry DNA Extraction

Cost: About $5 for strawberries and a bottle of rubbing alcohol; the other items are usually available around your home or workplace (and only needed in very small quantities)

Age Range: elementary-middle school

Difficulty: Easy to set up; explaining the procedure will take some staff preparation

Here’s what you’ll need:

 

1. The day before, put the bottle of rubbing alcohol in the freezer and keep it icy cold right up until you’re ready to use it.

2. Remove the stems from 2-3 strawberries, put them in a Ziploc bag and have the kids mash them up.

3. Create an “extraction buffer” with 1 cup water, 3/4 tsp. salt, and 3/4 tsp. dish soap or shampoo; add this solution to the mashed strawberry, and mash the bag well to mix it well.

4. Place the funnel over a glass, and a coffee filter into the funnel, and pour the mixture from the baggie into it; use a spoon to press as much through the filter as possible.

5. Carefully drop or pour the cold rubbing alcohol down the side of the glass. The mixture will separate into layers; the strawberry’s DNA is the white mucous-like substance on top. You can remove it with a craft stick or coffee stirrer to examine it more closely.

This activity works well in a program with a discussion about DNA in general, solubility of liquids, forensic investigations, or even gardening.

I learned about the procedure from Cool Forensic Tools by Esther Beck, 2009.