Separate RNA and DNA

by A. Untergasser (contact address and download at www.untergasser.de/lab)
Version: 1.0 - Print Version (.PDF)

ATTENTION: This is a low priced and well working protocol. Use it preferably!

  1. Dilute the DNA/RNA solution to 90 µl
  2. Add 30 µl 8M LiCl and mix well
  3. Store 30 min at -20 °C
  4. Spin 10 min at max speed at 4 °C
  5. Keep supernatant (DNA) and pellet (RNA)
  6. Wash RNA pellet with 100 µl 70% Ethanol
  7. Spin 10 min at max speed
  8. Dissolve the RNA pellet in 30 µl water
  9. Store the RNA solution at -80 °C
  10. Add 80 µl isopropanol to the supernatant containing the DNA
  11. Store 30 min at -20 °C
  12. Spin 10 min at max speed
  13. Keep the pellet (DNA)
  14. Wash DNA pellet with 100 µl 70% Ethanol
  15. Spin 5 min at max speed
  16. Dissolve the DNA pellet in 30 µl water
  17. Store the DNA pellet at -20 °C

Commented Protocol:

1. Dilute the DNA/RNA solution to 90 µl

Do not dilute RNA too much or the RNA will not precipitate and be lost.

2. Add 30 µl 8M LiCl and mix well

LiCl precipitates only the RNA.

3. Store 30 min at -20 °C

Some protocols incubate 2 - 4 h on ice, others 1 h at -80 °C.

4. Spin 10 min at max speed at 4 °C

5. Keep supernatant (DNA) and pellet (RNA)

6. Wash RNA pellet with 100 µl 70% Ethanol

7. Spin 10 min at max speed

8. Dissolve the RNA pellet in 30 µl water

Some protocols precipitate again with 1/10 vol of 3 M NaAc and 2.5 vol 100% ethanol and wash then the pellet again with 70% ethanol before dissolving it. I never found it necessary.

9. Store the RNA solution at -80 °C

10. Add 80 µl isopropanol to the supernatant containing the DNA

11. Store 30 min at -20 °C

Now we precipitate the DNA.

12. Spin 10 min at max speed

13. Keep the pellet (DNA)

14. Wash DNA pellet with 100 µl 70% Ethanol

15. Spin 5 min at max speed

16. Dissolve the DNA pellet in 30 µl water

17. Store the DNA pellet at -20 °C

Known Issues:

References and Comments:

This is a basic protocol commonly in use. It works very well even when compared with commercial kits.

How to cite this page in publications:

This document can be cited like this:

Untergasser A. “Separate RNA and DNA” Untergasser's Lab. Winter 2008. (include here the date when you accessed these page).
<http://www.untergasser.de/lab/protocols/separate_rna_and_dna_v1_0.htm>.

Please Do Not Reprint This Article:

This article is copyrighted. Please do not reproduce this article in whole or part, in any form, without obtaining my written permission.