Below is a link to a gel electrophoresis simulator, which will allow you to practice running gels without having to go through the long, messy process. You can add up to eight values for kilobase pairs, change the strength of the electric field, and alter the concentration of the gel agarose.
Go to the website and change the values of all the variables until you are able to predict the effect each will have on a gel run. Once you are able to do this, your ability to run an actual electrophoresis gel effectively will increase significantly. http://webphysics.davidson.edu/applets/biogel/biogel.html |