How to Extract DNA in 4 Steps

Have you ever wanted to see the code that makes you unique?

This summer, I got the chance to wear my DNA on my neck. 

This happened when I attended the Introduction to Biotechnology class offered by UC Berkeley's Academic Talent Development Program (ATDP). There, I extracted my DNA and put it into a little pendant where I could proudly boast my genetic code. We extracted DNA from my cheek, USDA organic farmers market strawberries, non-GMO oats, and even Cool Ranch Doritos. But before I teach you how to extract your DNA, we first need to understand what it is.

DNA (deoxyribonucleic acid) is the instruction manual for all living things. It instructs cells on how to build proteins, grow, and reproduce. Every plant, animal, fungus, and even bacteria has it. DNA is built on a few simple compounds bound together by weak hydrogen bonds. DNA is responsible for making you look like you. But here’s the thing, you don’t need a lab coat or a million-dollar microscope to extract DNA. You can do it right in your kitchen. With a few common materials and a basic understanding of science, anyone can extract DNA from something like a strawberry, a banana, or even their saliva.

At the core of DNA extraction is cell biology. Living cells are surrounded by membranes made of fats (lipids) and proteins. Inside those cells, DNA is coiled tightly in the nucleus. To access the DNA, you must break through both the outer cell membrane and the nuclear membrane. To do this, we use something called a lysis buffer. A lysis buffer is a solution used to break open cells. It typically contains detergents, salts, and other components that disrupt cell membranes. But when we open up cell membranes, all sorts of other organelles spill out. But we want only the DNA, so we put in a protease to break down the proteins and unwanted organelles. But DNA is very soluble, so we add salt so that it won't dissolve in the water and also clump together. But right now it just looks like water, which is why we need to add cold isopropyl alcohol. This will precipitate the DNA and make it visible. So let's learn how we can extract DNA at home.

Ingredients:

1. Your sample (a strawberry is most commonly used)

2. 1 resealable plastic bag

3. 2 tsp dish detergent

4. 1 tsp salt

5. 1/2 cup water

6. 1 coffee filter

7. 2 plastic cups

8. 1/2 cup rubbing alcohol(isopropyl or ethanol works)

9. 1 stirrer

First, put the sample inside a resealable plastic bag. You then need to mash the sample to break up the tissue and expose the cells. 

Then we need to make our homemade lysis buffer. First, gather ½ cup water in a small cup, then add 2tsp dish detergent and mix thoroughly. Next, add 1 tsp of salt and mix till the salt is dissolved in the solution. Then pour the lysis buffer into the plastic bag and mash with the solution inside. When we are mashing the bag, the salt is helping the DNA clump together later, while the soap breaks apart the cell and nuclear membranes. You can't see this, of course, because cells are so small that you would need a microscope to see them. 

Once the solution is smooth, this means the cells are broken open and the DNA is floating freely in the mixture. So we filter the solid pieces out. This can be done with a coffee filter or cheesecloth. 

Then comes the most exciting part, where you add cold alcohol (usually rubbing alcohol or ethanol). Make sure to slowly and gently pour the cold alcohol down the side of the container. The point of adding alcohol is to make it visible. This works because DNA doesn’t dissolve in alcohol, especially when it’s cold. So when the alcohol is poured gently down the side of the container, it forms a layer above the liquid extract. In that alcohol layer, white, stringy strands begin to appear. That’s the DNA. Keep in mind, this is the DNA from millions of cells, each containing billions of molecules of DNA.

The reason why this process works on most living material is that whether you use a banana or blood from a fish, all living things share the same basic cellular structure. This means whether you hold a mango or a leaf, its cells contain a cell membrane and DNA in its nucleus. When I did this experiment, strawberries worked the best. Strawberries work best because they have extra DNA compared to most plants (they’re octoploid, meaning they have eight copies of each chromosome), which makes the extraction especially visible.

Labs use similar methods to the ones in our experiment, except labs are just more refined and precise. But the principles of DNA extraction are the same: break open the cells, isolate the DNA, and make it visible. Whether you're a student, teacher, or just curious, extracting DNA is a hands-on way to understand the instruction manual inside you. Now you know that science isn’t just something locked behind lab doors but something you can do at home.