This first applet is mainly for fun. You can click on the applet to add restriction sites for A and B, then run the gel to see what it looks like:
Now that you have some experience under your belt, see if you can find the missing restriction site in the following applet:
Finally, can you figure out what plasmid could produce the following gel? (There are multiple correct answers — for example, you could add the second A site either clockwise or anti-clockwise. Just try to find one possibility).