Principle and Procedure of Nucleic Acid Separation by Agarose Gel Electrophoresis

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Agarose is isolated from the seaweed genera Gelidium and Gracilaria, and consists of repeated agarobiose (L- and D-galactose) subunits.
They are the most popular medium for the separation of moderate and large-sized nucleic acids (0.5- to 25-kb DNA fragments) and have a wide range of separation.
Agarose gel electrophoresis method is used in biochemistry, molecular biology, genetics, and clinical chemistry to separate a mixed population of macromolecules such as DNA, RNA or proteins in a matrix of agarose.
The protocol can be divided into three stages:
a gel is prepared with an agarose concentration appropriate for the size of DNA fragments to be separated;
the DNA samples are loaded into the sample wells and the gel is run at a voltage and for a time period that will achieve optimal separation; and
the gel is stained or, if ethidium bromide has been incorporated into the gel and electrophoresis buffer, visualized directly upon illumination with UV light.
Agarose gel electrophoresis is a method that separates biomolecules like DNA, RNA and proteins by applying an electric field to move them through an agarose matrix.
The percentage of agarose included in a gel impacts the pore sizes and thus the size of molecules that may pass through and speed at which they do so.
The principle of agarose gel electrophoresis is based on the idea that charged molecules will move towards an electrode with an opposite charge in an electric field.
Electric current causes the negatively-charged DNA to migrate towards the anodal, positive (+ve) end. The rate of migration is proportional to size: smaller fragments move more quickly and wind up at the bottom of the gel.