Swinging Girl

Extract DNA

Using simple items you have in your bathroom and kitchen, you can extract DNA from fruits like bananas, kiwi or strawberries.

 

 

What do I need to get started?

  • Fruit (banana, strawberry, kiwi, etc.)
  • Water
  • Rubbing alcohol (70% or higher) that is ice cold
  • Table salt
  • Plastic bag
  • Coffee filter
  • Chopstick, toothpick or paperclip
  • Clear glasses (or test tubes)

How to do the extraction

Before you begin, make sure you have chilled your alcohol in the freezer. This is a very important first step. Room temperature alcohol will not work nearly as well as cold alcohol. Pop the whole container in the freezer to chill it. The alcohol will not actually freeze!

The first thing you will need is a sample. Since DNA is found in all living things I’d suggest an inexpensive fruit like strawberries, kiwi or a banana. You probably already have something like this in your kitchen. The cool thing is you don’t need much material which means you can eat the fruit you don’t use.

The DNA is contained inside the nucleus of the cell. To release it, we need to break down the plant matter, then break open the cell and finally break in to the nucleus of the cell.

Your first step is to break apart the plant matter. That means squish up the fruit. This can be done in a glass with a spoon, but I think it’s easier and cleaner to do in a zip-top plastic bag. Add about 1/3 cup of fruit to the bag, remove the air, seal and then start squishing it up. That’s about 1/3 a banana, or two big strawberries or one whole kiwi. Once it’s turned into a paste set the bag aside.

Now we need something to break open the cell walls. It turns out that cell walls are make up of things called lipids, or fats. If you had greasy or fat coated dishes in the kitchen, you would use a detergent to clean it up. We are going to do the same thing to break open those cell and nuclei walls to release the DNA.

Fill a clear glass with 1/2 cup of water. Slowly add in 2 teaspoons of dish soap and 1/2 teaspoon of table salt. Gently mix this solution without making bubbles until the salt dissolves. The salt will latter help the DNA stick together.

Add this solution to your ziplock bag of squished up fruit. Don’t add to much liquid. Add enough so that you have a nice mixture that you cannot see through. That’s probably about 1/4 of a cup of soap solution. Flatten out your baggie to remove most of the air and then seal it up. Gently squish the liquid around. If you have the time, let this mixture sit for 10-20 minutes to give the detergent time to release a lot of DNA.

Filtering out the plant matter is the next step. Place a coffee filter on top of a glass and carefully pour your fruit mixture into the filter. You can gently squeeze the filter to get more liquid out, just don’t break it! This is the solution that contains the DNA. Since the DNA is soluble in water we need something else to sort of pull it out of the solution. For this we will use rubbing alcohol (ethyl alcohol will work as well).

You will want to use at least 70% alcohol for the extraction. The higher the concentration of alcohol the better it will work to make the DNA come out of the water solution.

Very carefully pour the alcohol down the side of the glass. You are trying to create a layer of alcohol that floats on the top of the water solution. The DNA will come out of solution at the boundary layer between the water and alcohol. You should see some white string almost cotton like strands begin to appear in the glass. That is the DNA!

Let the solution sit for a few minutes and you should see more DNA come out of the solution. You can collect the DNA using a toothpick, chopstick or paperclip. You have extracted DNA at home!

If you want to save your DNA you can store it in a small container filled with the rubbing alcohol.

Additional Activities

If you found this interesting, check out some our other activities!