Since we cannot see DNA without special dyes, we add a tracking dye to each reaction tube. This does not stain the DNA, but because of their size, the dye molecules move at a rate that is similar to that of the DNA. Sucrose or glycerol is also added to the mixture to make it dense enough to sink into the well.

Use a micropipette to load 5–10 µl from each reaction tube into a well. (Your instructor may vary this procedure and have you load the wells with DNA before you pour the buffer.)