How could gel electrophoresis be applied to the identification of a gene mutation?
Look a difference in the weights of bands compared to a control
As you know, gel uses electricity to separate bands of macro-molecular material by weight.
You'd start by running a control gel. Let's say your gene codes for some macro-molecule that is really big. Like it barely leaves the well. Then run your mutation. Is the band suddenly lighter and travels further? Is it heavier, does it stay even further up? If there is a weight change, specifically surrounding a band related to your gene of interest, like a protein it codes for, you'd say that that was evidence that there was a difference between samples.
Tl:DR You would see your protein (doesn't have to be protein) would be lighter or heavier than normal and point to that as proof something was off.