Question

Explain the steps involved in the formation of human insulin by transgenic E. coli.

Answer 1

Human insulin consists of two polypeptide chains, A and B, joined by disulphide bonds. In 1983, Eli Lilly used recombinant DNA technology to produce human insulin using E. coli.

Steps:

1. DNA sequences corresponding to the human insulin A and B chains were prepared separately.
2. Each sequence was inserted into a plasmid of E. coli, creating genetically modified bacteria.
3. The transgenic bacteria were cultured so that they produced the A and B chains separately.
4. The chains were extracted and purified from the bacterial cultures.
5. The purified chains were joined by disulphide bonds to form mature, functional human insulin.

This method produces human insulin without relying on insulin extracted from cattle or pigs, which could cause allergic or immune reactions in some patients.