Molecular Techniques – Isolation of Genetic Material and Gel Electrophoresis

Electrophoresis is a separating technique used to separate different biomolecules with positive and negative charges. Principle By applying electricity (DC) the molecules migrate according to the type of charges they have. The electrical charges on different molecules are variable.

Agarose GEL Electrophoresis

It is used mainly for the purification of specific DNA fragments. Agarose is convenient for separating DNA fragments ranging in size from a few hundred to about 20000 base pairs. Polyacrylamide is preferred for the purification of smaller DNA fragments. The gel is complex network of polymeric molecules. DNA molecule is negatively charged molecule – under an electric field DNA molecule migrates through the gel.

The electrophoresis is frequently performed with marker DNA fragments of known size which allow accurate size determination of an unknown DNA molecule by interpolation. The advantages of agarose gel electrophoresis are that the DNA bands can be readily detected at high sensitivity. T he bands of DNA in the gel are stained with the dye Ethidium Bromide and DNA can be detected as visible fluorescence illuminated in UV light will give orange fluorescence, which can be photographed.

a – bands of dna in agarose gel

b – Gel electrophoresis instrument

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