Question

Two DNA fragments are collected, i.e., A and B. Assuming that A contains more base pairs than B, select the incorrect statement with respect to gel electrophoresis if the DNA samples A and B are loaded in two wells.

• A. A will stay near the cathode than B
• B. B will migrate with a greater speed compared to A towards the anode
• C. A will migrate with a greater speed compared to B towards the anode
• D. Both A and B will form two distinct bands corresponding to their molecular weights

Answer 1

The correct option is C A will migrate with a greater speed compared to B towards the anode

Agarose gel electrophoresis is a technique that separates charged molecules of different sizes under the influence of an electric field. The rate of migration is determined by the size of the DNA molecule. The greater the size of a DNA molecule, the greater the resistance that it faces to percolate through the pores present in the agarose gel. Hence, a smaller sized DNA with a lesser number of base pairs and lower molecular weight travels more distance than a heavier one, under specific laboratory conditions.

Given that A has more base pairs than B. Since, they have different molecular weights, they will form distinct bands according to their molecular weights. Besides, A will migrate with a lesser speed compared to B. Hence, A will travel a lesser distance compared to B in a given time. Therefore, A will stay closer to the cathode (negative terminal) while B will form a band closer to the anode (positive terminal).