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. And we form three different fragments, as shown, that have these different sizes. Now, in case B, we take that same initial gene, but now we expose it to a different restriction enzyme which cuts at different locations along that gene. So now, instead of producing these three fragments, we only produce two fragments because this gene only contains one side, one location where this restriction enzyme number two can actually act on.