Science Buddies: "Ask an Expert"

I am running a gel electrophoresis and I was wondering how long it should take before the samples start moving

How quickly the samples move through a gel depends on the size of the DNA and the voltage applied. Larger DNA fragments migrate through the gel slower than smaller fragments. Theoretically, the moment an electrical current is applied to the gel box, the DNA samples should move. This is due to the negative charge of the DNA. However, you should keep in mind that you can't actually see the DNA moving through the gel. When you load DNA samples in the gel, this is done with a loading dye. Its the loading dye that you see moving through the gel. It is unlikely that you would see the loading dye move the moment you turn on electrical current.

If you are concerned about whether a current is actually being applied and the gel is really "running," an easy way to determine this is whether or not you see little bubbles coming up from the bottom of the gel box. These bubbles appear the moment you turn on the electrical current.

I hope this was helpful. Don't hesitate to ask if you have more questions!

Best,
Hannah