About This Lesson
Subjects
- Chemistry
- Biology
- Biotechnology
Time
- 45 -60 minutes
Skills
- 2D Design
- Design Thinking
- Problem-solving
- 3D Design
Learning Objective/Goal:
- Understand the basic structure and function of DNA.
- Learn a simple method for DNA extraction.
- Develop laboratory skills and scientific inquiry.
Materials Needed:
- Fresh strawberries (2-3 per group)
- Dish soap (1 tablespoon per group)
- Table salt (1/2 teaspoon per group)
- Isopropyl alcohol (Chilled, 1/2 cup per group)
- Ziplock bags (1 per group)
- Coffee filters (1-2 per group)
- Clear plastic cups or beakers (2 per group)
- Plastic pipettes or droppers
- Measuring cups and spoons
- Stirring rods or spoons
Background
- Strawberries are soft and easy to crush. They also have a lot of DNA, which makes them perfect for this experiment.
- Role of Each Material:
- The soap helps break open the cells to release the DNA.
- The salt helps separate the DNA from other parts of the cell.
- The cold alcohol makes the DNA come out of the liquid so we can see it. The colder the alcohol, the better it works, so keep it in the freezer or on ice.
- This is why strawberries are great for extracting DNA!
Activity
Part 1: Crushing the Strawberries
- Place 2-3 strawberries into a ziplock bag and remove as much air as possible before sealing.
- Mash the strawberries thoroughly for about 2 minutes until they become a smooth pulp.
Part 2: Preparing the Extraction Solution:
- In a clear cup, mix 10 mL of dish soap, 1/2 teaspoon of salt, and 1/2 cup of water.
- Add the extraction solution to the bag of mashed strawberries.
- Seal the bag and gently mix the contents for about 1 minute.
Part 3: Filtering the Mixture:
- Place a coffee filter over a second clear cup or beaker.
- Pour the strawberry mixture into the coffee filter and allow the liquid to filter through into the cup. This may take a few minutes.
- Use this time to explain how each step is helping to extract DNA
Part 4: Extracting the DNA:
- Once the liquid has filtered through, carefully add an equal amount of chilled isopropyl alcohol to the cup. Pour it down the side of the cup to form a layer on top of the strawberry liquid.
- Wait for a few moments and observe. White, stringy DNA will begin to form at the interface between the strawberry liquid and the alcohol.
Part 5:
- Use a plastic pipette or a stirring rod to gently spool the DNA and transfer it to a small container or observe it on the rod.
Extra
Tips for Students:
- Be gentle when mixing and filtering to avoid breaking the coffee filter.
- Carefully observe during the DNA precipitation step to see the formation of DNA strands.
Tips for Teachers:
- Pre-chill the alcohol well in advance.
- Demonstrate each step before allowing students to proceed.
- Encourage students to ask questions and think about the purpose of each step in the process.
References and more information:
