Easy DNA Extraction from Saliva
Fun Science Experiment for High School Students
In this simple and engaging laboratory experiment, you'll learn how to extract DNA from saliva using household items. DNA extraction is a fundamental technique used in biology and genetics research to isolate DNA for various analyses. Saliva, a readily available biological sample, contains cells with DNA, making it an ideal source for genetic experiments.
Saliva samples are commonly used in genetic testing services like 23andMe. These tests analyze DNA extracted from saliva to provide insights into ancestry, traits, and health predispositions. Saliva contains cells with DNA, making it a convenient and non-invasive source for genetic analysis.
Materials Needed:
- Saliva sample
- Small tube or cup
- Dishwashing liquid
- Table salt
- Rubbing alcohol (isopropyl alcohol)
- Water
- Small funnel (optional)
- Clear plastic cup or glass
Procedure:
1. Collecting the Saliva Sample:
- Spit into a small tube or cup until there's enough saliva (about 1-2 tablespoons).
2. Breaking Open the Cells:
- Pour a little bit of dishwashing liquid (about a teaspoon) into the saliva and mix gently for a minute. This helps break open the cells.
3. Adding Salt:
- Add a pinch of table salt and mix again. Salt helps the DNA stick together.
4. Filtering Out Debris (optional):
- If you want, you can pour the mixture through a small funnel into a clear plastic cup or glass to filter out any solid bits.
5. Precipitating the DNA:
- Pour rubbing alcohol slowly down the side of the cup or glass until there's about the same amount of alcohol as saliva mixture. Don't mix!
- Let it sit for a few minutes. You'll see white stringy stuff form at the top – that's the DNA!
6. Collecting the DNA:
- Gently scoop out the DNA using a toothpick or the end of a paperclip. It might look like snot or slime.
Notes:
- Be careful not to mix the rubbing alcohol with the saliva mixture too much – you want them to layer on top of each other.
- The DNA you collect can be stored in a small container or plastic bag and kept in the fridge for a little while if you want to show it off or use it for experiments later.
- Have fun and be curious! DNA extraction is a cool experiment that helps you learn about the building blocks of life.
Discussion
- What role do each of the household items play in the DNA extraction process, and how do they contribute to isolating DNA from saliva?
- How does the appearance of the extracted DNA compare to your initial expectations? Were there any surprises or unexpected observations during the experiment?
- Discuss the significance of using saliva as a source of DNA in genetic testing compared to other biological samples, such as blood or tissue samples.
- How might variations in the DNA extraction process, such as adjusting the amount of dishwashing liquid or salt used, impact the yield or quality of the extracted DNA?
- Reflect on the broader implications of DNA extraction techniques in scientific research and real-world applications, such as forensics, medicine, and conservation biology. What ethical considerations should be taken into account when working with DNA samples?
Other Resources on DNA
Strawberry DNA Extraction - instructions for extracting DNA from a strawberry, very simple, works every time!
DNA Investigation with Strawberries (basic) - simplified version of DNA extraction lab for intro level, with minimal equipment
Investigation: DNA Extraction for AP Biology - students extract DNA from different samples and write a lab report; with Claim, Evidence and Reasoning
Coloring DNA - basic image of DNA and RNA for students to color following directions; includes questions and analysis