Isolation of the DNA (or gene of interest) followed by the separation of digested fragment of the DNA is one of the crucial steps of Recombinant DNA Technology. The separation is based on the technique called gel electrophoresis.
Gel electrophoresis is a method for separation and analysis of macromolecules (DNA, RNA and proteins) and their fragments, based on their size and charge.
The separated DNA segments are stained with ethidium bromide for visualisation after exposure to UV light in gel electrophoresis. Bright orange coloured bands of DNA can be observed in the gel when exposed to UV light. The separated bands of DNA are cut out from the agarose gel and extracted from the gel piece. This step is called elution. Chromogenic substance are used as a selectable marker.