DNA Isolation from Banana
Introduction
DNA (Deoxyribonucleic acid) is the hereditary material found in all living organisms, carrying genetic information that governs growth, function, and reproduction. Isolating DNA from simple sources like fruits is a widely used classroom activity to demonstrate the presence of DNA in cells. Banana is an ideal choice because it contains a large amount of DNA that can be easily extracted and visualized. By using common household materials such as detergent, salt, and alcohol, we can break open banana cells, release DNA, and make it visible to the naked eye as a white, thread-like substance.
Precautions
- Use fresh, ripe bananas for best results.
- Handle alcohol carefully; it should be chilled for effective DNA precipitation.
- Avoid contamination by using clean containers and tools.
- Do not ingest any of the experimental materials.
- Dispose of the waste responsibly.
Materials Required
- Ripe banana (½ piece)
- Blender or zip-lock bag
- Salt (1 teaspoon)
- Dishwashing detergent (2 teaspoons)
- Water (½ cup)
- Muslin cloth
- Test tube or transparent glass
- Ice-cold rubbing alcohol/ethanol (½ cup)
- Stirring stick
Science Behind It
Banana cells, like all living cells, contain DNA inside the nucleus. To isolate DNA, the cell wall and membranes must be broken open, and proteins and other molecules separated from DNA. The process involves three key steps:
- Cell Lysis: When the banana is mashed and mixed with detergent, the detergent disrupts the lipid bilayer of cell membranes and nuclear membranes, releasing DNA into the solution.
- Salt Action: Salt helps to neutralize the negative charges on DNA molecules and causes them to clump together, making DNA less soluble in water. It also helps separate DNA from proteins that may be bound to it.
- DNA Precipitation: When cold alcohol is carefully layered on top of the solution, DNA, which is insoluble in alcohol, precipitates out. This makes DNA visible as a cloudy, white, stringy substance.
This experiment demonstrates how basic chemistry can make something invisible at the microscopic level become visible. It provides a simple but powerful way to understand the structure and function of DNA, the universal genetic code that connects all living organisms—from bananas to humans.