Banana extraction lab

Banana Extraction Lab
Printable version: Banana2.02.V3

Objectives
– Practice measuring and weighing solids and liquids
– Apply the steps of DNA extraction
– Reinforce good lab technique and safety
– Practice good experimental recording procedures in the lab notebooks

Materials:
­ Banana
­ Distilled water (cold)
­ Table salt
­ Meat tenderizer
­ Isopropyl (rubbing) alcohol (cold)
­ Dish detergent
­ Ice to chill water and alcohol
­ 50ml Falcon tube
Equipment/Labware:
­ Beakers
­ Graduated cylinders
­ Scale
­ Blender
­ Sieve
Glass stirring rod

The purpose of this lab is to extract DNA from a banana. You will cover the steps of a DNA extraction and see them in action. These same steps are used when extracting DNA for experimental research, forensic science, etc.

DISRUPTION

  1. 1 banana, 500-1000 ml cold water, 1 g table salt
    1. Blend or mash the banana and salt with the water to make a slurry
    2. Strain through sieve to remove large chunks
    3. Distribute in Erlenmeyer flasks

LYSIS: detergent

  1. Add 2 ml dishwashing detergent to each flask of banana/salt solution
    1. Swirl gently to mix without creating a lot of bubbles
    2. Transfer approximately 20 ml to each student in a 50 ml plastic Falcon tube
    3. Let sit at room temperature for 5-10 minutes, stirring occasionally

LYSIS: enzymatic

  1. Add 500 mg of meat tenderizer to the detergent/banana solution
    1. Stir gently for 2 minutes

PRECIPITATION:

  1. Holding the test tube at an approximately 45° angle, GENTLY pour in rubbing alcohol. It is important that the rubbing alcohol doesn’t get mixed in with the banana solution. This creates two phases: aqueous and non-aqueous. DNA is water-soluble, but is insoluble in alcohol
    1. DNA will come out of solution and form as a filmy white substance in the alcohol layer
    2. Use the glass stirring rod to gently lift the DNA out of the liquid, it will look like egg whites.

Additional Experiments:
DNA can be extracted from almost anything. Other popular sources for this protocol are onions, strawberries, peas, and chicken livers. It may help to use a blender for the disruption step when working with tougher plant materials.

Questions:

  1. Why do we need to extract DNA?
  2. What is the purpose of each of these steps?
  3. Where is the DNA in each of these steps?
  4. Do you think you could get DNA out of 1) nuts, 2) leaves, 3) wood, 4) plywood, or 5) paper? Why or why not?
  5. What do you think will happen if you put the DNA in water? Why?