What technique is used to separate DNA fragments?
Electrophoresis is the motion of dispersed particles (like DNA fragments) relative to a fluid under the influence of a spatially uniform electric field.
DNA electrophoresis is an analytical technique used to separate DNA fragments by size.
DNA molecules which are to be analyzed are set upon a viscous medium, the gel, where an electric field forces the DNA to migrate toward the positive potential, the anode, due to the net negative charge of the phosphate backbone of the DNA chain.
The separation of these fragments is accomplished by exploiting the mobilities with which different sized molecules are able to traverse the gel. Longer molecules migrate more slowly because they experience more drag within the gel. Because the size of the molecule affects its mobility, smaller fragments end up nearer to the anode than longer ones in a given period