How to extract DNA from a banana

What is DNA?

DNA is an important part of every living thing. It is found in every single cell of every living thing. DNA is the molecule that carries all the information about how an organism looks and functions. For example, the specific information that your DNA carries is what determines what colour your eyes and hair are. A strand of DNA (like the image on the right) is only 0.000002 mm wide; that’s 35,000 times thinner than an average strand of human hair! Because it’s so small, we need to collect a lot of DNA before we can see it with our naked eyes.

Extracting DNA from a banana

Materials:

  • 1 ripe banana
  • ½ cup tap water
  • ¼ teaspoon table salt
  • 1 teaspoon dish soap
  • 2 tablespoon tap water
  • ~2-3 tablespoon ice cold 99% alcohol (isopropyl alcohol or ethanol work well)
  • 1 plastic bag (or other container for mashing a banana)
  • 1 coffee filter
  • 2 clear glasses
  • 1 spoon
  • 1 skewer or piece of wire
  • 1 tube or container to hold your DNA
  • Optional string and decorations to make a DNA necklace

Instructions:

  1. Peel the ripe banana and put it in the plastic bag.
  2. Add ½ cup of table water to the plastic bag, and mash your banana until it is a smooth consistency.
  3. Add ¼ teaspoon of table salt, 1 teaspoon of dish soap, and 2 tablespoon of tap water to a glass, and stir gently with a spoon until the salt and soap are dissolved. This will take a few minutes.
  4. Add 2 tablespoon of the banana mixture to the same glass, and stir for at least 10 minutes.
  5. Place the coffee filter into the second glass, and secure it with an elastic band.
  6. Pour the contents of the first glass (banana/soap/salt mixture) into the coffee filter. Allow the liquid to drain through the coffee filter. The liquid that collects in the glass below the coffee filter is called the filtrate. This will take between 10 and 15 minutes. Do not squeeze the coffee filter, as it might rip.
  7. Estimate the volume of the filtrate, and add a similar amount of ice cold alcohol. Do not stir. Leave the mixture undisturbed for about 5 minutes. You should start to see a white solid forming in the glass. This is your DNA!
  8. Use a skewer or piece of wire to collect the DNA from the glass, and add it to the tube or container you have prepared to store your DNA.

Add a string to your tube, and turn it into a necklace, keychain, ornament...!