How is genetic engineering used to create bacteria capable of producing human insulin?

In a production of human insulin by bacteria the human insulin gene is incorporated into the genetic material of these microorganisms. A Mutant bacterium multiplies forming lineages of insulin-producing bacteria.

In the bacteria there are circular strands of DNA called plasmids, minichromosomes which act as an accessory to the major DNA. To create the mutant bacteria capable of producing insulin a plasmid is submitted to the action of restriction enzymes (restriction endonucleases) specialized in cutting DNA fragments. Once a circular plasmid is open by the restriction enzyme. The similar enzyme is used to cut a human DNA molecule containing the insulin gene and the piece of human DNA containing the insulin gene then has its extremities bound to the plasmid with the help of DNA ligases and the recombinant plasmid containing the human insulin gene is then inserted into the bacteria.

A further human hormone already produced by recombinant bacteria is GH (growth hormone or somatotropin).

The insertion of the DNA molecules into cells of an individual is also the method of the gene therapy, a promising treatment for genetic diseases. In the gene therapy cells from an organism deficient in the production of a given protein receive (by means of vectors, for example virus) pieces of DNA containing the protein gene and they then begin to synthesize the protein.