Materials
- 2 ripe strawberries
- 1 small zip-top bag
- 1 tablespoon dish soap
- ½ teaspoon table salt
- 3 tablespoons water
- ¼ cup (60 mL) isopropyl rubbing alcohol (70%, kept in the freezer for at least 30 minutes)
- Cheesecloth
- Clear glass or small cup
- Toothpick, wooden stick, or skewer
- Measuring spoons
- Funnel
Instructions
- Remove the green tops and place the strawberries in a zip-top bag. Seal the bag.
- Mash the strawberries for 1–2 minutes until they become a smooth, pulpy mixture.
- In a small cup, mix 3 tablespoons water, 1 tablespoon dish soap, and ½ teaspoon salt, stirring gently until the salt dissolves.
- Pour this extraction solution into the bag with the mashed strawberries. Seal the bag again.
- Mix by gently squishing the bag for another 1–2 minutes, avoiding foam.
- Place a small piece of cheesecloth over the top of a clear glass in a funnel to act as a simple strainer.
- Carefully pour the strawberry mixture through the cheesecloth into the glass.The cheesecloth only catches large chunks, the liquid can still be a bit cloudy.
- Take the very cold rubbing alcohol out of the freezer.
- Slowly pour ¼ cup (60 mL) of alcohol down the side of the glass, letting it form a separate clear layer on top of the strawberry liquid.
- Wait a few minutes. At the boundary of the two layers, you will see white, stringy, cloudy clumps forming.
- Insert a toothpick or wooden skewer into the boundary where alcohol meets strawberry liquid. Gently swirl. The DNA will stick to the toothpick and spool up as white, thread-like strands.
- Lift the toothpick out to see visible strawberry DNA!
What’s going on?
- To see strawberry DNA, you need to break open the cells and pull the DNA out of solution:
- Mashing breaks the tissue apart. Dish soap dissolves cell and nuclear membranes (made of lipids), releasing DNA. Salt helps separate the DNA from proteins and makes the DNA molecules clump together. Cold alcohol makes the DNA precipitate (it comes out of solution because DNA does not dissolve in cold alcohol).
- The white, stringy material you spool onto the toothpick is real, visible strawberry DNA!
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