DNA EXTRACTION FROM CALF THYMUS
(adapted from lab by Mr. Pigeon)

Instructions:
  1. Homogenize the mixture (small piece of calf thymus and prep buffer) in a blender.

  2. Centrifuge (slow speed) and KEEP supernatant (upper portion which contains DNA). Centrifuge this supernatant again until a nuclear pellet (whitish colour) is visible in bottom of test tube. Keep the nuclear pellet and discard the liquid on top.

  3. Re-suspend the pellet in fresh prep buffer in a small test tube and mix gently with a clean glass rod. This becomes the nuclear suspension.

  4. Collect about 40 drops of the nuclear suspension (from step 3) in another small test tube.

  5. Add 20 drops of EDTA (let sit for 5 min.). This weakens the nuclear membrane and inhibits DNAses to prevent DNA degradation.

  6. Add 6 drops of SDS (let sit for 1 min.). This dissolves membrane lipids and separates histones (proteins) from DNA.

  7. Slowly add 6 drops of NaCl solution to the test tube. Pause after every drop and gently mix in a slow, circular movement. Then very gently transfer to a small beaker (the DNA is fragile).

  8. Add enough ice-cold ethanol to double the volume already in the beaker. Very carefully run the alcohol down a clean glass rod into beaker. This separates DNA from proteins and the DNA forms a whitish precipitate.

  9. Insert a glass rod into the DNA layer (lower layer) and rotate the glass rod to spool a whitish precipitate. This is DNA. If the DNA is of high purity it will be pure white or somewhat iridescent like an opal.