a. Eli Lilly prepared two DNA sequences corresponding to the A and B chains of human insulin.
b. Sticky ends were produced in the Escherichia coli plasmid and the insulin gene by treating them both with the same restriction endonucleases.
c. These two are then joined together by the enzyme DNA ligase.
d. The bacteria are then grown in sterilised bioreactors in the appropriate growth medium.
e. The chains A and B are produced separately, extracted and purified.
f. These two chains are then combined by creating disulfide bonds to form human insulin.