In agarose gel electrophoresis, the DNA fragments are separated under

The correct option is A the influence of electric field
Gel electrophoresis is a laboratory technique based on the principle of movement of charged particles towards oppositely charged electrodes under the influence of electric fields. The technique is widely used for the separation of a mixture of DNA (a negatively charged molecule) fragments of varying sizes on agarose gel (a natural biopolymer) matrix under the influence of electric field.

The end of the electrophoresis unit with an electrode connected to the negative terminal of the power supply has a negative charge (cathode) while that connected to the positive terminal of the power supply carries a positive charge (anode). The gel is placed in the electrophoretic unit such that the wells with loaded DNA samples are placed towards the negative electrode. When the current is allowed to pass, the DNA molecules, being negatively charged, are forced to migrate towards the oppositely charged pole, i.e., anode.
Additionally, the pore size of the gel is a determinant of the degree of migration. The pores present in the gel create a sieving effect and help in the separation of DNA molecules based on their size. The smaller the molecules are in size, the greater the distance they can migrate in the gel.


Diffusion refers to the movement of molecules from a region of their higher concentration to that of lower concentration. Though diffusion can lead to slight movement of DNA molecules over prolonged hours, it cannot drive accurate separation of fragments of varying sizes.

Neither heat nor light are applied externally to the gel to drive the migration of DNA molecules. Additionally, excess heat can interfere with the proper migration and separation of DNA fragments by destroying cross linkage in the gel.