Practice question

Migration velocity in gel electrophoresis is described by electrophoretic mobility balanced against frictional drag. Factors include net charge, molecular size, buffer ionic strength, voltage gradient, and gel matrix friction. The gel matrix provides molecular sieving; larger molecules experience greater obstruction and lower mobility. Gel color or sample volume does not fundamentally alter mobility per molecule, though excessive volume broadens bands. Voltage polarity determines direction, not rate magnitude. Therefore, friction from gel matrix, proportional to gel concentration and crosslinking, critically regulates molecular migration rate.