Insulin (Figure 3.41) was the first protein to be sequenced biochemically. Assuming that there were no introns involved in the process, what are the possible DNA sequences that produced the last four amino acids in the molecule (shown in bold)?

Bovine insulin consists of two polypeptide chains that are joined by two disulfide bonds (-SS). Hydrogen bonds also exist between the chains and between segments of the same chain. The three letter names stand for different amino acids

|F| J| | | ||6|x| |k|| | _9 Val - Glu TyrLeu Leu Ala Phe-Gly-Arg Leu Val |J|K||||5|5 Cys-S-S-Cys