Prepare your samples for electrophoresis while the gel is curing by adding concentrated loading buffer. The loading buffer contains two dyes, bromophenol blue and xylene cyanol. During electrophoresis, the dyes will migrate with “apparent” molecular weights of ~5 kb and ~0.5 kb, respectively. The loading buffer also contains glycerol, which makes the sample dense enough to sink to the bottom of the sample well.
Add 4 μL of 6X loading buffer directly to each of the 20 μL PCR reactions from the last lab. Briefly, centrifuge each tube to mix the dye and samples, if necessary. You will use half of each sample in your gels. Store the remaining sample in the refrigerator.