Insulin is composed of two protein chains, the A chain, which has 21 amino acids, and the B chain, which has 30 amino acids. The protein is synthesized as a larger precursor molecule in which the following segments of the molecule are found, in order: signal chain + A chain + C peptide + B chain. The signal chain, which consists of 24 amino acids, is first removed. Then the C peptide is removed, and the A and B chains are linked together.

In insulin mRNA, the protein coding sequence has 318 nucleotides. How many amino acids would be translated from this sequence? How many amino acids would be in the C peptide?

The A chain of the protein includes the sequence glutamate-cysteine-cysteine-alanine (glu-cys-cys-ala or ECCA, using the single letter amino acid designations). Which of the following DNA coding sequences would encode this segment of the protein?

a.) CCCCCGCAGAAG
b.) GGCATCGTGGAG
c.) GAGTGCTGTGCC
d.) CTGCCCCGACAC
e.) GTCACGACACGG