DNA Extraction from a Plant Sample

 

Experiment No: 3 - DNA Extraction from a Plant Sample

Objective:

To extract and observe DNA from a plant sample, such as spinach, strawberries, or bananas, using a simple laboratory procedure.

Materials:

• Fresh plant sample (e.g., spinach leaves, strawberries, or bananas)
• Mortar and pestle
• SDS
• Salt (sodium chloride)
• Distilled water
• Ethanol (chilled in a freezer)
• Cheesecloth
• Test tubes or small beakers
• Glass rod or wooden skewer (for DNA spooling)
• Measuring Cylinder

Procedure:

1. Preparation of the Plant Sample:

• Homogenization: Place a small amount of the plant sample (about 2-3 grams) into a mortar. Add a small amount of distilled water (about 10 ml) and a pinch of salt (about 1 gram). Grind the sample with the pestle until a smooth paste is formed.
• Transfer: Pour the homogenized mixture into a test tube or small beaker.

2. Lysis of Plant Cells:

• Add Detergent: Add about 2 ml of dish soap or detergent to the plant mixture. This step helps to break down the cell membranes and nuclear envelopes, releasing the DNA into the solution.
• Mix Gently: Stir the mixture gently to avoid creating bubbles. Allow it to sit for about 5-10 minutes.

3. Filtration:

• Filter the Mixture: Place a cheesecloth over a clean test tube or beaker. Pour the mixture through the filter to remove the solid plant debris, leaving behind a liquid containing the DNA.

4. Precipitation of DNA:

• Add Cold Ethanol: Tilt the test tube or beaker slightly and carefully pour an equal amount of cold ethanol down the side of the container so that it forms a layer on top of the aqueous plant mixture. Do not mix the layers.
• Observe DNA Precipitation: DNA will precipitate out of the solution and form a white, cloudy substance at the interface between the ethanol and the plant extract. This may appear as a stringy or clumped substance.

5. DNA Collection:

• Spool the DNA: Use a glass rod or wooden skewer to gently spool (twist) the DNA by slowly rotating the rod at the interface of the two layers. The DNA will adhere to the rod and can be lifted out of the solution.

Observations:

• Appearance of DNA: Describe the appearance of the extracted DNA. It may appear as a white, stringy, or clumpy substance.
• Yield: Estimate the amount of DNA extracted. This can vary based on the plant sample and the efficiency of the extraction process.

Conclusion:

The experiment successfully demonstrates the extraction of DNA from plant cells. The procedure involves breaking down the cell walls and membranes using physical grinding and chemical detergents, followed by the precipitation of DNA using cold ethanol. The visible DNA extracted provides a hands-on understanding of the molecular material that carries genetic information in all living organisms.

Precautions:

• Use cold ethanol to ensure efficient DNA precipitation.
• Handle the plant material and chemicals carefully to avoid contamination.
• Ensure gentle mixing to prevent shearing of the DNA, which can affect its visibility and texture.
• Perform the experiment in a clean environment to avoid contamination of the DNA sample.

This experiment provides a simple and effective method for isolating DNA from plant tissues, allowing for a visual appreciation of genetic material and the processes involved in its extraction.