Now, since DNA fragments are all negatively charged, they all move along the same direction. They always move from the cathode, the negatively charged side, to the anode, the positively charged side. And this voltage difference is created because this entire structure is connected to a battery source. So this is what gel electrophoresis is. So the way that we create the restriction map is by exposing this initial gene to many different types of restriction enzymes. For example, in case A, we expose the gene to restriction enzyme number one.