Easy DNA Extraction

Just follow these seven simple steps to find DNA!

Deoxyribonucleic acid or DNA 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.

Materials:

While you can use any DNA source, some work especially well – finely chopped onions, are excellent choices. Do not use DNA from living people or pets, as a simple matter of ethics.

2 onions, coarsely chopped 125 mL distilled or cold water, ½ cup

1 mL table salt or NaCl, ⅛ tsp

30 mL concentrated liquid dishwashing detergent

1 mL fresh pineapple juice or contact lens leaning solution isopropyl alcohol, refrigerated

  • knife
  • cutting board
  • blender
  • strainer
  • 250 mL measuring cup or Erlenmeyer flask
  • clear bowls or test tubes
  • straws, wooden skewers or glass stirring rods

Directions for the DNA Extraction:    

  1. Peel and cut onion in eights, and place onions in blender.  Add salt, 125 mL (½ cup) water; adding extra 15 mL (1Tbsp) if required for good blending. Blend coarsely – about 5 seconds. If you puree the onion too finely, the  filtering step will be very slow. The blender breaks apart the cells, releasing the DNA that is stored inside.  
  2. Line strainer with paper towel or coffee filter and place strainer over cup or beaker. Pour the onion/salt/
  3. water solution into the lined strainer. Strain liquid from onion mixture. This should take about 10-15 minutes. The goal is to remove the chunks from the liquid. 
  4. Pour liquid into glass bowl or beakers. Add 50 mL (¼ cup) liquid soap. Stir gently to prevent creating a foamy mess.  Let soap incubate with onions for 5 minutes. Salt and soap act to strip away proteins normally bound to DNA. The detergent also separates the fats from the sample. 
  5. Divide liquid contents into 5 clear plastic cups, bowls or test tubes. Add 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.  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.
  6. Tilt each container and gently drizzle the isopropyl alcohol along the sides of the container, 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. 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.
  7. Examine the interface between soap solution and isopropyl alcohol, and look for some white stringy stuff – DNA!  Allowing light to shine through the container will make it easier to see the DNA. Allow the mixture to sit for a few minutes, and an increasing amount of DNA will come out of solution.
  8. Wait approximately 5 minutes. Mix gently with straw or stirring rod – long strands of DNA should spool onto rod.
  9. Examine the DNA using a microscope or magnifying glass or place it in a small container of alcohol to save it.

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