Insulin, synthesized by the beta cells of the islets of Langerhans, consists of two dissimilar polypeptide chains, A and B, which are linked by two disulfide bonds. The gene contains 3 exons and 2 introns; exon 2 encodes the signal peptide, the B chain, and part of the C peptide, while exon 3 encodes the remainder of the C peptide and the A chain.
