This procedure will teach you how to isolate DNA from biological samples like saliva. Basically what we will do is open up the cells with soap, deteriate proteins with salt and precipitate the DNA with alcohol. Using the centrifuge, the DNA will stick to the bottom of our tube for us to get rid of the rest.

Materials

  • Dish soap, hand soap or shampoo
  • 10% Salt solution
  • Alcohol, 95% like Spiritus is great, otherwise Vodka will also work
  • Small glass
  • 2 mL centrifuge tubes
  • Mixing rod / tooth pick

Equipment

  • Centrifuge
  • Transfer pipettes

Procedure

  • Collect a few spits of saliva in a small beaker glass
  • Add a few drops of soap and mix a little with the rod
  • Transfer 1 mL the mixture into a 2 mL centrifuge tube
  • Add 1 mL of 10% salt solution and mix again
  • Centrifuge the tube at 10.000 rpm for 5 minutes
  • Transfer two times 1 mL of the supernatant into two fresh centrifuge tube
  • Add 1 mL of ice cold ethanol to each tube
  • Centrifuge the tubes at 10.000 rpm for 10 minutes
  • Dispose of the supernatant, the pellet contains your DNA

You may wash the pellet a few times if you like by repeating the procedure.

Return to BHA2 - Class 5