Principle:
The process includes:
1. Cell Lysis: Crushing the banana breaks open its cells.
2. Membrane Disruption: A solution containing soap and salt is added. The soap dissolves cell membranes, releasing DNA, while the salt helps the DNA strands come together.
3. Filtration: The mixture is filtered to remove large particles, leaving a solution with DNA.
4. DNA Precipitation: Cold alcohol is added to the filtered solution. DNA is not soluble in alcohol, so it precipitates, becoming visible as a white, stringy substance.
Procedure:
1. **Prepare the Banana Mixture:**
- Peel and mash a ripe banana thoroughly.
- In a cup, mix 1 teaspoon of clear liquid soap and 1/4 teaspoon of table salt with 2 tablespoons of distilled water. Stir gently to avoid foam.
- Add 2 tablespoons of the mashed banana to the soap solution. Stir the mixture gently for about 10 minutes.
2. **Filter the Mixture:**
- Place a coffee filter over a clean cup and pour the banana mixture into it. Allow the liquid to pass through, collecting the filtrate in the cup. This may take several minutes.
3. **Extract the DNA:**
- Obtain a test tube containing cold isopropyl alcohol (chilled by placing in ice water).
- Carefully add the filtered banana solution to the test tube with cold alcohol.
- Let the test tube sit undisturbed for about 4 minutes. DNA will precipitate out as a white, stringy substance.
- Use a thin glass rod or a plastic pipette to gently spool or collect the DNA.
This method allows you to see the DNA that is present in the cells of the banana.
For a visual demonstration, you can watch the following video: