- Homogenize the mixture (small piece of calf thymus and prep buffer) in a blender.
- 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.
- 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.
- Collect about 40 drops of the nuclear suspension (from step 3) in another small test tube.
- Add 20 drops of EDTA (let sit for 5 min.). This weakens the nuclear membrane and inhibits DNAses to prevent DNA degradation.
- Add 6 drops of SDS (let sit for 1 min.). This dissolves membrane lipids and separates histones (proteins) from DNA.
- 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).
- 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.
- 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.