Question

in electrophoresis, the dye added is usually the type that migrates ahead of the protein molecules contained in the sample, why is this necessary?

Answer 1

You don't want your sample to run clean through the gel and out the other end. The dye runs faster than the gel. So as long as the dye is still on the gel, your proteins are still on the gel. Which is good. If the proteins run faster than the dye, you have no way of knowing they haven't run off the other end.

Answer 2

thanks blues...

Answer 3

Sure, you're welcome. :D