DNA Agarose Gel Electrophoresis

Agarose gel electrophoresis is a technique commonly used to separate DNA molecules by their size.

Agarose — a polysaccharide derived from red algae —  is added to a buffer such as Tris-acetate EDTA (TAE) or Tris-borate EDTA (TBE) and dissolved by heating.

Commonly, 1 gram of agarose is dissolved in 100 milliliters of buffer to form a 1% agarose solution, though different amounts of agarose can be added depending on the application.

To stain the gel, a fluorescent dye, such as ethidium bromide, is often added to the agarose solution. The dye intercalates between the DNA bases and fluoresces under UV light.

The solution can then be poured into horizontal molds. A comb is inserted into the gel cast to create wells into which DNA samples can be loaded.

The agarose solution is left undisturbed to solidify into a gel.

The gel consists of hydrogen-bonded agarose molecules forming a porous matrix through which the DNA molecules move.

DNA samples are mixed with a loading buffer and loaded on the gel. The loading buffer contains glycerol, which increases the density of the DNA samples and helps them settle at the bottom of the wells.

The buffer also contains dyes, such as xylene cyanol and b