Eli Lilly, in 1983, developed human insulin using recombinant DNA Technology by combining chain A and chain B with:

Disulfide bonds

The correct answer is Option (4) → Disulfide bonds

Insulin is composed of two short polypeptide chains, chain A and chain B, connected by disulfide bridges.  In 1983, the American pharmaceutical company Eli Lilly successfully created two DNA sequences corresponding to the A and B chains of human insulin. These DNA sequences were inserted into plasmids, which were then introduced into Escherichia coli (E. coli) bacteria. Inside the E. coli cells, the A and B chains of insulin were produced independently as separate protein molecules. After extracting the A and B chains from the bacterial culture, they were combined and linked together through the formation of disulfide bonds, resulting in the creation of fully functional human insulin. This achievement marked a significant milestone in medicine, as it enabled the production of human insulin using recombinant DNA technology, revolutionizing the treatment of diabetes worldwide.