1. Prepare and label fresh, sterile 1.5 ml eppendorf tubes.
2. Remove the tubes containing cell/DNA lysates from a 55°C shaker, or a water bath, to which they were placed on Day 1, and let them cool down.
3. Centrifuge the tubes at 14,000xg, at RT for 5 minutes.
4. Carefully remove the supernatants, which now contain human, genomic DNA, and place them in fresh, sterile tubes.
5. Add equal volume of ispopropanol to the supernatants, mix by inverting the tubes and let the DNA precipitate at RT for 10 minutes. Precipitated DNA should become visible in a tube resembling a small piece of white thread.
6. Centrifuge the samples at 14,000xg, at RT for 5 minutes.
7. Carefully remove the ispopropanol away from the DNA pellet. Add 1 ml of 70% ethanol (which should be prepared with sterile, ultra-pure H2O) to DNA pellets. Gently mix by inverting the tubes several times.
8. Centrifuge the samples at 14,000xg, at RT for 5 minutes. Remove the ethanol and air-dry DNA pellets for approximately 10 minutes. Ensure that no droplets of ethanol are left in the tubes by removing them carefully with a sterile pipette tip.
9. Add 50 μl of sterile 1xTE buffer (10mM Tris-HCl, pH 8.0, 1mM EDTA, pH 8.3), pre-warmed at 55°C, to every DNA pellet, in order to dissolve genomic DNA sample. Vortex to dislodge the pellet away from the wall of the tube.
10. Place the tubes at 55°C for 10 minutes, with gentle shaking, if possible.
11. Merge two of three tubes of every individual DNA samples into one.
12. Centrifuge the merged human, genomic DNA samples at 14,000xg, at RT for 1 minute, in order to pellet the undissolved DNA.
13. Place the supernatant containing the dissolved, human, genomic DNA into a fresh, sterile 1.5 ml eppendorf tube.
13. Determine the concentration of the DNA in tubes.
14. Freeze down the 3rd tube containing the individual DNA sample, without removing the pellet. Keep this as a backup DNA sample.