How many amino acids does each codon code for in the genetic code?

Draw the structure of a four-residue segment of DNA with the following sequence. (3′end) G-T-A-C (5′ end)

For the enzyme isopentenyl pyrophosphate isomerase, IPP binds tightly as a result of interactions between the active site amino acid residues and the diphosphate of IPP. Without concerning yourself with the structure of amino acids, what charges might you expect to be present in the active site to hold IPP in place so that the enzymatic reactions can occur?