Dr. Green: Director of the National Human Genome Research Institute
Dr. Easter: Education Specialist at the National Human Genome Research Institute
Purpose: To show how to isolate DNA from strawberries using household items.
Why Use Strawberries for DNA Isolation?
Attributes of Strawberries:
Pleasant smell and visual appeal
Edible fruit with seeds on the outside
Ease of Extraction: Strawberries are a suitable choice due to their high DNA content and ease of access, making it simple to demonstrate the DNA extraction process.
Steps for Isolating Strawberry DNA
Step 1: Prepare the Strawberries
Use frozen strawberries for easier processing due to their softer texture.
Place strawberries in a plastic bag to crush them and release the DNA stored within the cells.
Step 2: Create the Lysis Solution
Lysis: To break open the strawberry cells.
Materials Needed:
2 teaspoons of detergent (for breaking up the cell membranes)
1/2 teaspoon of salt (to help stabilize the DNA)
1/2 cup of water
Mixing: Stir gently to avoid excessive bubbles which can complicate the extraction process.
Step 3: Mixing Strawberries with Lysis Solution
Combine strawberry puree with the lysis solution and gently mix to avoid excessive bubbles.
Allow the DNA to go into solution as the cell membranes break open.
Step 4: Filtering the Mixture
Filtration: Use a regular coffee filter to separate the liquid (containing DNA) from solid strawberry debris.
Pour the strawberry mixture into the coffee filter slowly to avoid tearing.
Step 5: Precipitate the DNA
Precipitation: A method to make the dissolved DNA visible.
Add Rubbing Alcohol: Pour an equal amount of rubbing alcohol into the filtered liquid.
Alcohol causes the DNA to precipitate out of the solution, forming a visible layer of DNA.
Observation: After mixing, a gunky, slimy layer will form at the interface of the two liquids, which consists of the extracted DNA.
Step 6: Collecting the DNA
Use a popsicle stick to spool the DNA for observation.
DNA appears as a white, slimy substance, free from red strawberry residue.
Applications of Isolated DNA
Analysis: The extracted DNA can be analyzed similarly to methods used in forensic testing.
Medical Relevance: The techniques learned can apply to isolating DNA from various biological samples like blood or cheek cells, with implications for medical diagnosis and treatments.
Storing the Isolated DNA
Recommended to store the DNA in a sealed container (like a zip-lock bag or small tube) in the refrigerator for longevity.
Conclusion
Encouragement for Experimentation: Students can replicate the experiment at home by following detailed instructions available on the National Human Genome Research Institute's website.
Final Note: The process is not only educational but also illustrates the relevance of DNA in health and medicine, encouraging curiosity and understanding of genetics.