Simple Protocol on DNA Extraction from Onion Cells

An easy protocol for demonstration of DNA to students. Not even a centrifuge is required.
Aim: To isolate DNA from onion
Materials Required:
  • Onion bulbs
  • Extraction solvents: 50ml liquid detergent (labolene), 11.25g NaCl in 1000ml distilled water
  • Isopropyl alcohol or 95% ethanol kept on ice
  • Cheese cloth (4 thicknesses)
  • Water bath
  • Ice bucket
  • Beaker, glass rod, test tubes etc
dna exaction from onion
1. 10g of fresh peeled onion is weighed out and ground with mortar and pestle to breakdown the cell wall.
2. Add 20 ml extraction and grind well to release cell contents.
3. Transfer to a test tube and Incubate in a water bath at 50-600C for 15 minutes
4. Immediately incubate in ice water for 5 minutes
5. Filter through 4 layers of cheese cloth
6. To 3 ml filtrate, add 5 ml ice cold iso-propanol along the sides of the test tube without shaking
Keep this test tube undisturbed for 3-5 minutes in ice
White strands of DNA migrate from the filtrate to the alcohol layer
6. Using a glass rod spool the DNA out
7. Transfer the DNA to micro centrifuge tube and stored in TE buffer
Observation: Cloudy white strands of DNA appear in alcohol layer
Note: This protocol is not suitable for getting pure DNA for molecular biology experiments


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