How to Extract DNA From Any Cell

DNA or deoxyribonucleic acid is the molecule that codes genetic information in most living organisms. Some bacteria use RNA for their genetic code, but any other living organism will work as a DNA source for this project. It's easy to extract and isolate DNA, which you can then use for further experimentation.

DNA Extraction Materials

While you can use any DNA source, some work especially well. Peas, such as dried split green peas, are an excellent choice. Spinach leaves, strawberries, chicken liver, and bananas are other options. Don't use DNA from living people or pets, as a simple matter of ethics. Be certain your sample actually contains a lot of DNA. Old bones or teeth or shells consist mainly of minerals and only traces of genetic material.

• 100 ml (1/2 cup) of a DNA source
• 1 ml (⅛ teaspoon) table salt, NaCl
• 200 ml (1 cup) cold water
• Enzymes to denature protein (e.g., meat tenderizer, fresh pineapple juice, or contact lens cleaning solution)
• 30 ml (2 tablespoons) liquid dishwashing detergent
• 70-90% rubbing alcohol or other isopropyl or ethyl alcohol
• Blender
• Strainer
• Cup or bowl
• Test tubes
• Straws or wooden skewers

Perform the DNA Extraction

1. Blend together 100 ml of DNA source, 1 ml of salt, and 200 ml of cold water. This takes about 15 seconds on high setting. You are aiming for a homogeneous soupy mixture. The blender breaks apart the cells, releasing the DNA that is stored inside.
2. Pour the liquid through a strainer into another container. Your goal is to remove the large solid particles. Keep the liquid; discard the solids.
3. Add 30 ml liquid detergent to the liquid. Stir or swirl the liquid to mix it. Allow this solution to react for 5-10 minutes before proceeding to the next step.
4. Add a small pinch of meat tenderizer or a squirt of pineapple juice or contact lens cleaner solution to each vial or tube. Swirl the contents gently to incorporate the enzyme. Harsh stirring will break the DNA and make it harder to see in the container.
5. Tilt each tube and pour alcohol down the side of each glass or plastic to form a floating layer on top of the liquid. Alcohol is less dense than water, so it will float on the liquid, but you don't want to pour it into the tubes because then it will mix. If you examine the interface between the alcohol and each sample, you should see a white stringy mass. This is the DNA!
6. Use a wooden skewer or a straw to capture and collect the DNA from each tube. You can examine the DNA using a microscope or magnifying glass or place it in a small container of alcohol to save it.

How It Works

The first step is to choose a source that contains a lot of DNA. Although you can use DNA from anywhere, sources high in DNA will yield more product at the end. The human genome is diploid, meaning it contains two copies of each DNA molecule. Many plants contain multiple copies of their genetic material. For example, strawberries are octoploid and contain 8 copies of each chromosome.

Blending the specimen breaks apart the cells so you can separate the DNA from other molecules. Salt and detergent act to strip away proteins normally bound to DNA. The detergent also separates the lipids (fats) from the sample. The enzymes are used to cut the DNA. Why would you want to cut it? The DNA is folded and wrapped around proteins, so it needs to be freed before it can be isolated.

After you have completed these steps, the DNA is separated from other cell constituents, but you still need to get it out of solution. This is where the alcohol comes into play. The other molecules in the sample will dissolve in alcohol, but DNA does not. When you pour alcohol (the colder the better) onto the solution, the DNA molecule precipitates so that you can collect it.

Sources

• Elkins, K.M. (2013). "DNA Extraction". Forensic DNA Biology. pp. 39–52. doi:10.1016/B978-0-12-394585-3.00004-3. ISBN 9780123945853.
• Miller, D.N.; Bryant, J.E.; Madsen, E.L.; Ghiorse, W.C. (November 1999). "Evaluation and optimization of DNA extraction and purification procedures for soil and sediment samples". Applied and Environmental Microbiology. 65 (11): 4715–24.