Given all of the years that I have spent teaching children to cook and eat healthy, it comes as no surprise that I like to include food in my high school biology curriculum. Right now, we are finishing up a unit on cell division and DNA. My students were thrilled to find a large mug filled with strawberries on my desk this week on our lab day. But they couldn’t get over the strange mixture of odors – the sweet fragrance of the berries combined with the vapors evaporating from our bottles of rubbing alcohol. Like a fruit-doctor’s office!
The goal of our lab was to extract the DNA from the berries, so they could see what it looks like with the naked eye. It was simple to do, and can even be done at home with kids of any age.
The best part was that we didn’t need any fancy-schmancy scientific equipment to complete the lab. We only required a combination of ingredients and equipment that most households have handy. (I know you probably don’t have a test tube – but I have a hunch that you have a shot glass!).
To set up the lab, we started by combining the mashed berries with a soap, salt and water mixture, which breaks down the phospholipid cell membranes. Then we filtered the sludge through a double layer of cheesecloth. One student suggested that we could have even used a coffee filter instead.
After our filtrate was collected in a test tube, we added cold rubbing alcohol, which repelled the DNA molecules so they clumped together into a clear glob (somewhat similar to egg whites or mucus).
Then, we used a thin plastic loop to spool up the DNA and look at it. If you were doing this lab at home, you could use a long wooden toothpick or bbq skewer. (You know a lab is awesome if the kids ask if they can take out their phones to take photos!)
You can download a copy of the lab that I used with my students here: Strawberry DNA Extraction Lab. For all 5 of my biology classes, I used this recipe to make the soap/salt buffer solution: 900 ml. water, 50 ml dish soap and 2 tsp salt. At home, you would need to reduce it significantly for a much smaller portion.
Additional photos from this lab are posted to my class Facebook page.