Final answer:
Agarose is used in gel electrophoresis to form a gel matrix that separates DNA or RNA molecules by size and shape, with the pore size of the gel determined by the concentration of agarose used.
Step-by-step explanation:
In gel electrophoresis, agarose is used as a solid medium to separate DNA or RNA molecules based on size and shape. Agarose, a polysaccharide extracted from seaweed, forms a gel matrix with pores when mixed with a buffer and cooled. This matrix creates a molecular sieve that impedes larger molecules more than smaller ones as they move through the gel under the influence of an electric field.
The percentage of agarose used determines the pore size of the gel, with higher percentages resulting in smaller pores, suitable for separating smaller molecules. As an analytical tool, it can be employed to evaluate the success of restriction endonuclease reactions, which alter DNA conformation and as such affect how far DNA fragments migrate. Preparatively, it can be used to purify specific DNA fragments post-cutting.