Extracting DNA from a strawberry is a fun and easy science experiment! Here's how to do it:
Materials Needed:
- Strawberries: Fresh or frozen (remove green leaves). Strawberries are ideal because they are octoploid, meaning they have eight sets of chromosomes, making DNA extraction easier.
- Resealable plastic bag: A quart-sized bag works well.
- DNA extraction liquid: This is typically made by mixing dish detergent (to break down cell membranes), salt (to help DNA clump together), and water. A common recipe uses 2 teaspoons of dish detergent, 1 teaspoon of salt, and ½ cup of water.
- Rubbing alcohol (isopropyl alcohol): Cold is best. This is used to precipitate the DNA, making it visible.
- Strainer or cheesecloth: To filter the strawberry mixture.
- Glass or small beaker: To collect the filtered mixture.
- Small stirring rod: To gently stir the mixtures.
Procedure:
- Prepare the Strawberries: Place the strawberries (remove any green leaves) in the resealable plastic bag. Gently crush the strawberries for about two minutes to break open the cells and release the DNA. This initial step is crucial for DNA release.
- Add the Extraction Liquid: Pour the prepared DNA extraction liquid into the bag with the crushed strawberries. Seal the bag and gently mix thoroughly. The detergent breaks down cell and nuclear membranes, releasing the DNA.
- Filter the Mixture: Pour the strawberry mixture through a strainer or cheesecloth into a glass or beaker. This removes larger plant debris, leaving a clearer mixture containing the DNA.
- Add the Alcohol: Slowly pour the cold rubbing alcohol down the side of the glass, creating a layer on top of the strawberry mixture. Avoid mixing the layers.
- Observe the DNA: You'll observe a white, cloudy substance appearing at the interface between the strawberry mixture and the alcohol. This is the strawberry DNA! It precipitates out of the solution because it's insoluble in alcohol.
Understanding the Process
The detergent in the extraction liquid breaks down the cell membranes, releasing the cell's contents, including the DNA. The salt helps to clump the DNA molecules together, making them easier to see. The cold alcohol then causes the DNA to precipitate out of the solution, making it visible as a white, stringy substance.
Tips and Troubleshooting
- Use cold alcohol for better DNA precipitation.
- Gently mix the solutions to avoid breaking the DNA strands.
- If you don't see much DNA, you may need to adjust the amounts of the ingredients in your extraction liquid or let the mixture sit longer.
