Electrophoresis gels: the race track
You need a track if you’re going to race and the electrophoresis gel is the molecular race track. The track is a gel matrix that is similar to a slab of gelatin. The electrophoresis gel is made by adding a powdered substance such as agarose (Fig. 1) to water, bringing the water to a boil, and then allowing the solution to cool. Agarose will form a gel matrix as it cools, conforming to the shape of the container or mold. The matrix will have spaces that are filled with the water. The size of these spaces depends upon the concentration and physical properties of agarose. Change the concentration or switch to a different substance (acrylamide for example) and you alter the size of the holes or spaces in the matrix. Therefore, a matrix made from agarose and water is the race track used to compare the speed of DNA from different samples.