Combine the gel loading solution with DNA digests to both visualize the sample run and to make the sample sink into the well. This dense, buffered solution contains two dyes. Bromphenol blue migrates at the same rate as a 200-400 base pair DNA fragment, at the beginning of a typical run. Xylene cyanole migrates at the same rate as a 4,000 base pair DNA fragment and helps visualize the middle to end. Usually add 1 µL of the gel loading solution for every 5 µL of digest.