Pulsed-field gel electrophoresis.

DNA molecules in an agarose matrix elongate and migrate toward the anode when exposed to an electric field. An agarose matrix represents a highly irregular network with pores of various dimensions, large open areas, and regions with different densities. During electrophoresis, migration will be retarded by obstructions that prevent sieving by size and result in "end-on" migration as if through a sinuous tube ("reptation" [1]). The limit of resolution is reached when the radius of gyration of the linear DNA exceeds the pore size of the gel.