Gel Electrophoresis

Nucleic acids come in a very wide range of sizes, from several dozen base pairs to many millions. No single technique can be used to separate them all. Instead, researchers analyze the nucleic acid molecules using the overlapping electrophoretic techniques of polyacrylamide, agarose, and pulsefield gel electrophoresis. Each technique places DNA or RNA molecules in an electric field. Because the nucleic acid fragments contain negatively charged phosphate groups along the backbone of the DNA molecule, they move toward the positively charged anode. As with proteins, the migration rate of nucleic acids through a gel depends on their conformation, the buffer composition, the concentration of the gel support, and the applied voltage.