Extracting DNA

• describe the method for extracting DNA?

  • mash/grind sample in mortar and pestle with salt (break down cell wall, salt breaks H bonds between DNA and H2O molecules)
  • sieve sample to remove solid substances
  • add detergent (rupture cell membranes)
  • add protease (to uncoil DNA - breaks down the proteins the DNA is wound tightly around)
  • add ethanol - slow enzyme action, also helps to keep sample at cooler temperatures
  • use a wooden/glass stick to remove DNA
  • test sample with universal indicator paper - should be acidic
• why should the temperature be kept low throughout the DNA extraction procedure?

  • so enzymes don’t begin the breakdown DNA (reduces activity of hydrolytic enzymes)
• why does the detergent break down cell membrane?

  • detergent is amphipathic and can interfere with the bonds between phospholipids
  • phospholipids form suspension in aqueous solution
• is DNA an acid?

  yes