DNA Extraction from Banana
Biology Grade XII
Extracting DNA from Banana Cells
Objectives: After completing this experiment, students are expected to be able to:
- Explain the purpose of DNA extraction.
- Identify the function of each reagent.
- Observe DNA that has been released from banana cells.
- Explain why DNA appears as white threads.
Background
Every living organism stores genetic information in the form of DNA. Normally, DNA is located inside the nucleus. By breaking the cell membrane with detergent, removing proteins with salt, and adding cold alcohol, DNA separates and becomes visible as white, thread-like fibers.
Materials
- ½ ripe banana & 100 mL water
- 1 tsp salt & 2 tsp liquid detergent
- Ice-cold 95% ethanol
- Cheesecloth, funnel, beaker, test tube, & stirring rod
Safety Rules
- Wear gloves and safety goggles.
- Do not taste any materials.
- Handle cold alcohol carefully (flammable).
Procedure
- Prepare Solution: Mix water, salt, and detergent.
- Mash: Mash banana, add solution, mix for 2-3 mins.
- Filter: Filter mixture into a beaker.
- Transfer: Pour 10 mL into a test tube.
- Add Alcohol: Slowly pour cold alcohol down the side.
- Observe: Watch for white threads and spool with a rod.
Observation Table
| Observation | Description |
|---|---|
| Color of filtrate | - |
| Appearance after alcohol | - |
| DNA color/texture | - |
Questions: Understanding the Experiment
- Why is detergent used in DNA extraction?
- What is the function of salt?
- Why must the alcohol be very cold?
- Why does DNA become visible after alcohol is added?
- Which step would most likely fail if detergent were omitted? Explain.
- Why are ripe bananas commonly used for DNA extraction?
Data Analysis
Complete the table below based on your observation:
| Material | Function |
|---|---|
| Banana | |
| Detergent | |
| Salt | |
| Cold ethanol | |
| Filter |
Conclusion
Write a summary of your findings here:
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