In this laboratory session, participants will perform DNA extraction from a banana, applying basic laboratory techniques. The experiment will introduce participants to key concepts in molecular biology, focusing on the role of different chemicals in breaking down cell membranes and precipitating DNA. This hands-on activity reinforces the understanding of DNA’s presence in living organisms and the methods used to isolate it.
Educational Goals
- DNA extraction knowledge: Participants will learn about the role of detergents, salts, and alcohols in breaking down cellular structures and precipitating DNA.
- Practical laboratory Skills: This session will build competence in measuring liquids, handling glassware, and using laboratory balances, providing a strong foundation in basic scientific methodology.
- Data observation and documentation: Participants will develop skills in accurately observing and recording the outcomes of the experiment, fostering critical thinking and the ability to analyze scientific results.
- Conceptual application: This lab applies theoretical concepts from biology, particularly cell structure and function, through a tangible, real-world example.
This experiment not only emphasizes the fundamentals of molecular biology but also provides an engaging practical experience. Participants will extract and observe DNA, gaining an appreciation for the presence of genetic material in everyday objects and understanding the role of key substances in biological research.
Protocol
Preparation of the extraction solution
1. Ensure the balance is level using the adjustment screw.
2. Measure 30 mL of distilled water using a 70 mL graduated cylinder.
3. Transfer the distilled water into a 50 mL beaker.
4. Weigh the empty weighing dish on the balance and record its mass.
5. Adjust the balance sliders to the combined mass of the dish plus 5.4 g of sodium chloride (NaCl).
6. Using a 2.5 mL spatula, add sodium chloride to the dish until the balance needle aligns with zero.
7. Pour the sodium chloride into the beaker containing the distilled water.
8. Stir the mixture with a glass stirring rod until the salt is fully dissolved.
9. Add 10 drops of dish soap to the beaker.
10. Stir the solution again with the glass rod to ensure uniform mixing.
DNA extraction procedure
11. Place a piece of banana into a mortar.
12. Mash the banana thoroughly with a pestle until a thick, homogeneous paste is formed.
13. Slowly add the prepared extraction solution from steps 1–10 to the banana paste in the mortar, mixing well to ensure even distribution.
14. Secure the clamp on a universal stand.
15. Place filter paper into a funnel.
16. Using the clamp and stand, position the funnel over a test tube.
17. Filter the banana mixture into the test tube, filling approximately one-third of the tube (about 15 mL).
18. Measure 10 mL of cold methanol using a 10 mL graduated cylinder.
19. Slowly pour the methanol down the side of the test tube. The volume of methanol should be roughly double that of the filtrate.
20. Gently mix the contents of the test tube using a glass stirring rod. Avoid shaking the test tube to prevent disturbing the solution.
Anticipated Outcomes
This laboratory activity on DNA extraction from a banana is designed to give participants hands-on experience with molecular biology techniques. The following outcomes are expected from this lab session:
- Visualization of DNA: Participants will successfully extract and observe the DNA from banana cells. The DNA will appear as a white, gelatinous precipitate, resembling a stringy or jelly-like substance. While they will not be able to see the double-helix structure, they will clearly identify the physical presence of DNA as a collection of strands.
- Understanding the function of reagents: Participants will learn the specific role of each reagent in the DNA extraction process. Dishwashing soap will help break down the cell membrane by dissolving the lipids, allowing the contents of the cells to be released. Sodium chloride will help clump the DNA strands together by neutralizing the negative charges on the DNA molecules, and methanol will cause the DNA to precipitate out of the solution.
- Recognition of cellular structure: Through this process, participants will gain insight into how cells are structured and how their components, such as DNA, can be separated from the rest of the cellular material. This experiment reinforces the idea that DNA is found in every living cell and can be isolated using simple methods.
- Practical laboratory skills: Participants will improve their ability to use laboratory tools such as balances, graduated cylinders, mortars, pestles, and filtration systems. They will also practice precise measurement and mixing techniques, which are foundational skills in biological and chemical sciences.
- Critical thinking and hypothesis validation: By predicting the appearance of DNA and comparing their observations to their initial hypotheses, participants will develop skills in scientific reasoning and analysis. This reinforces the concept of forming hypotheses and validating or refining them through experimentation.
- Collaboration and documentation: Participants will work in groups to complete the experiment, promoting teamwork and communication. They will also document their process and observations carefully, developing essential scientific recording skills, which are vital for accurate reporting and future references in research.
This lab provides a comprehensive introduction to DNA extraction, equipping participants with both theoretical knowledge and practical skills. By the end of the experiment, participants will have a better understanding of the molecular structure of living organisms and the processes used in genetic research.
Lessons Learned:
- Technical skills: Participants will enhance their laboratory skills by mastering techniques such as accurate liquid measurements, balance use, and the preparation of chemical solutions. Additionally, they will gain experience in filtration and gentle mixing, both critical for preserving the integrity of delicate samples like DNA. These foundational skills are essential in any biological or chemical research setting.
- Scientific methodology: The lab emphasizes the scientific process, from hypothesis formation to data collection. By extracting DNA and observing the chemical reactions involved, participants practice careful observation and precise documentation of results, reinforcing the principles of reproducibility and reliability that are at the core of scientific research.
- Molecular biology insight: Participants will directly engage with the fundamental concept that DNA is present in all living organisms, using a hands-on approach to isolate and visualize this genetic material. This tangible experience with molecular biology deepens their understanding of cellular structure and the processes required to extract and observe DNA.
- Practical application of chemical reactions: This lab illustrates the practical role of chemicals—such as detergents, salts, and alcohols—in breaking down cell membranes and facilitating DNA precipitation. By witnessing the reactions firsthand, participants gain insight into the mechanics of molecular biology and the role of different reagents in manipulating cellular components.
- Appreciation of biological complexity: Isolating and observing DNA allows participants to connect with the building blocks of life, fostering a greater appreciation for the complexity and efficiency of biological systems. This hands-on interaction can inspire curiosity and a deeper respect for the molecular structures that drive life at every level.
- In conclusion: This laboratory exercise goes beyond simple DNA extraction—it provides participants with a deeper connection to molecular biology, teaching them the role of essential chemicals in biological processes, while strengthening their technical and observational skills. The experiment encourages a greater appreciation of the intricate workings of cellular mechanisms, reinforcing theoretical knowledge with practical application. Through this immersive experience, participants develop a holistic understanding of life at the molecular level, inspiring respect for the interconnectedness of biological systems and the scientific processes used to study them.
Summary of Assignment by Grade Range
Grades 3-5 (Ages 8-10)
- Focus: Introduction to basic laboratory techniques and understanding DNA as the building block of life.
- Activities
- Measuring and mixing simple solutions.
- Extracting DNA from a banana using common household materials.
- Observing the appearance of DNA after precipitation.
- Following simple safety instructions for handling chemicals.
Grades 6-8 (Ages 11-13):
- Focus: Intermediate understanding of molecular biology and hands-on application of DNA extraction.
- Activities
- Preparing and using the extraction solution (water, salt, detergent).
- Conducting the DNA extraction process step-by-step.
- Understanding the role of each reagent in the extraction process.
- Documenting observations of DNA formation and recording procedural steps.
- Following detailed safety protocols for handling chemicals like methanol.
Grades 9-12 (Ages 14-18):
- Focus: Advanced understanding of DNA extraction principles and critical analysis of molecular biology processes.
- Activities
- Mastering the preparation of extraction solutions and conducting DNA extraction with precision.
- Analyzing the function of detergents, salts, and alcohols in cell membrane breakdown and DNA precipitation.
- Detailed observation and analysis of the chemical reactions involved in DNA isolation.
- Meticulous documentation of the experimental process and outcomes.
- Adhering to advanced laboratory safety procedures and best practices for handling chemicals.
Laboratory essentials
Instruments
Triple beam balance
Mortar & pestle
Spatulas & tweezers
Glass rod
Funnel & filter
50mL test tubes
Beaker (50 ml)
Graduated cylinders
Metal stand & clamps
1 mL dropper
Products
Banana slices
NaCl (crystals)
CaSO4 (powder)
Methanol (liquid)
Dish soap (liquid)