DNA extraction from agarose gels (Paper-strip)

Contributed by Matt Lewis <hop2kin@yahoo.co.uk>

Paper strip method for DNA extraction from agarose gels

• Using a scalpel blade, cut a slit immediately in front of the band to be extracted.

Do not remove the band from the gel

• Cut a piece of filter paper (e.g. 3MM paper) to size to fit inside the slit.

For example, 3mm x 10mm

• Place the paper strip in the slit, return the gel to the electrophoresis tank (submerged in buffer) and switch on the current for 2–5 minutes.

The DNA runs onward into the paper and is delayed in the smaller mesh size of the paper. Eventually the DNA will pass through so you have to keep checking it under long-wavelength UV so as not to leave it too long.

• Remove the strip of paper (carrying at least some of the DNA) and place into a 0.5ml microfuge tube, DNA side down.
• Make a tiny hole in the bottom of the tube using a needle (CAREFUL!)
• Place the 0.5mL tube inside a 1.5mL tube and spin for 30 seconds.

You may have to remove the lid of the 1.5mL tube. The buffer and DNA are retained in the larger tube. You can add 100µL of TE to the paper and re-spin to get a little more DNA out.

• Phenol/chloroform extract and ethanol precipitate the DNA. Re-dissolve the DNA pellet in an appropriate volume of water or TE buffer (e.g. 10µL).

*The pellet is often so small that it is invisible *

This method is based, with permission, on an original protocol available here.