Strawberry DNA Extraction

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★☆ Some safety precautions required to perform safely

Categories: Mixtures and Separation, Cells and Microscopes, Forensics

Alternative titles: See DNA with the Naked Eye

Summary

By crushing strawberries and treating them with detergent, salt, and alcohol, students can extract visible strands of DNA. The detergent breaks open the cells, salt keeps proteins separate, and alcohol causes DNA to clump so it can be seen with the naked eye.

Procedure

Place strawberries in a resealable plastic bag and mash them thoroughly.
Add dishwashing liquid and salt to the bag and mix gently to release DNA from the cells.
Pour the mixture through a strainer or cheesecloth into a clear container.
Slowly add cold alcohol (such as isopropyl or ethanol) to form a layer on top of the strawberry liquid.
Wait a few minutes for white, stringy DNA to appear at the boundary between the two layers.
Use a stick or pipette to gently lift and collect the visible DNA strands.

Links

How to extract DNA from strawberries - National Human Genome Research Institute:

📄 Strawberry DNA extraction activity - The University of Queensland: https://imb.uq.edu.au/strawberry-dna-extraction-activity

Variations

Try extracting DNA from other fruits such as kiwis or bananas.
Compare how well different detergents or soaps work.
Test the effect of using cold versus room-temperature alcohol.

Safety Precautions

Wear safety glasses to protect eyes from splashes.
Handle alcohol carefully and keep away from flames.
Wash hands thoroughly after the experiment.
Dispose of materials safely - do not consume the mixture.

Questions to Consider

Why does detergent help release DNA from cells? (It breaks down cell membranes, releasing the contents.)
What role does salt play in the process? (It prevents proteins from sticking to the DNA.)
Why is alcohol necessary for this experiment? (DNA is insoluble in alcohol, so it clumps together and becomes visible.)
Why are strawberries particularly good for DNA extraction? (They are soft, easy to mash, and have multiple sets of chromosomes, providing lots of DNA.)