Ethanol Precipitation of DNA

• 3 M sodium acetate pH 5.2 or 5 M ammonium acetate
• DNA
• 100% ethanol

1. Measure the volume of the DNA sample.
2. Adjust the salt concentration by adding 1/10 volume of sodium acetate, pH 5.2 (final concentration of 0.3 M) or an equal volume of 5 M ammonium acetate (final concentration of 2.0 to 2.5 M). These amounts assume that the DNA is in TE only. If DNA is in a solution containing salt, adjust salt accordingly to achieve the correct final concentration. Mix well.
3. Add 2 to 2.5 volumes of cold 100% ethanol (calculated after salt addition). Mix well.
4. Place on ice or at –20°C for more than 20 minutes.
5. Spin a maximum speed in a microfuge for 10–15 min.
6. Carefully decant supernatant.
7. Add 1 mL 70% ethanol and mix spin briefly.
8. Carefully decant supernatant.
9. Air dry or briefly vacuum dry pellet.
10. Resuspend pellet in the appropriate volume of TE or water.