Steps in the production of insulin using recombinant DNA technology

1 The DNA that codes for insulin is purified and inserted into a plasmid,
which is circular DNA isolated from, for example, the bacterium E. coli.

2 The plasmid is enzymatically cut at predetermined sites using restriction
enzymes so that the chain is opened.
3 Insulin DNA can be attached to the chain, and the chain is closed
again.
4 The resealed, recombinant plasmid is introduced into a
bacterium, usually E. coli, and the modified E. coli will now
produce, in culture, human insulin.
It should be mentioned that the strain of E. coli used needs to be one
that lacks the enzymes that could digest the insulin produced by the bacterial
cell.