Question

Which of the following is FALSE regarding gel electrophoresis?

A. Sodium dodecyl sulphate is added to the protein sample so as to

give the proteins a net negative charge

B. Once the power supply is switched on, the proteins loaded into the

wells of the polyacrylamide gel will migrate from cathode to anode

C. Sample are loaded into the stacking gel and separation of proteins

only takes place in the resolving gel

D. Tracking dyes are often used to monitor protein migration

Answer 1

All of the statements here are TRUE.

SDS is added to the protein sample so that it can mask intrinsic charges of the protein and coat it in negative charge. The net charge of protein samples becomes negative in this way.

The negatively charged proteins move from the cathode (- charged electrode) towards the anode (+ charged electrode).

The polyacrylamide gel contains two segments, the stacking gel and the separating/resolving gel. The sample is loaded into the stacking gel where the multiple proteins get stacked one after the other. They get separated according to their sizes (molecular weights) only in the resolving gel.

Tracking dye like bromophenol blue is added to the sample mixture in order to track the migration of protein within the gel (proteins cannot be seen by themselves).