e negative charge of DNA molecules propels them through the electrical field toward the positive electrode. Shorter DNA molecules can travel farther in an agarose gel in a given amount of time than longer counterparts. Agarose gel electrophoresis provides a means of analyzing DNA by separating molecules based on size. However, in and of itself, agarose gel electrophoresis does not provide a means of visualizing the DNA. That role is played by two dyes: ethidium bromide and loading buffer.