Question

Given below is the apparatus of agarose gel electrophoresis. Match the labels with the most suitable alternatives given below.

• A. A- Sample well, B- Electrophoresis tank, C- Buffer solution, D- Power supply
• B. A- Electrophoresis tank, B- Sample well, C- Power supply, D- Buffer solution
• C. A- Electrophoresis tank, B- Sample well, C- Buffer solution, D- Power supply
• D. A- Sample well, B- Electrophoresis tank, C- Power supply, D- Buffer solution

Answer 1

The correct option is D A- Sample well, B- Electrophoresis tank, C- Power supply, D- Buffer solution

Agarose gel electrophoresis is a laboratory technique based on the principle of movement of charged particles (here DNA) in agarose matrix towards oppositely charged electrodes (anode) under the influence of electric field. The DNA molecules (negatively charged) present in a mixture are of varying sizes. Hence, these travel different distances while migrating towards the positive terminal (anode) on the gel in an electric field. This is obtained in the form of bands after ethidium bromide staining and UV visualisation.

The agarose gel electrophoresis apparatus has the following components:

Gel casting tray: It is the tray where the gel is placed.

• The gel is composed of agarose dissolved in buffer solution (TAE or TBE) by heating followed by cooling.
• The gel contains wells which are dug using combs. The DNA sample is loaded inside wells.

Electrophoresis unit/ tank: It is the plastic unit inside which the gel is placed.

• It has two terminals, employed as anode (positive terminal) and cathode (negative terminal).
• It is flooded with a buffer solution to ensure proper ionic conduction.

Power supply: It provides the voltage to create an electric field of suitable strength. This exerts the driving force to carry the negatively charged DNA molecules towards the anode.