And by piecing together, by determining the order of the fragments, we can then determine what the order of the sequence of nucleotides is in that long DNA molecule. Now, we can also use restriction enzymes to create recombinant DNA molecules and then we can actually clone and amplify those molecules if we want to. And there are many other purposes, as we'll see in the next several lectras. Now let's move on to the mechanism of action. How exactly does this cleaving process take place? So restriction enzymes are these proteins found in these natural biological system cells.