Genetic modification allows for insulin to be made quickly and cheaply on a large scale, the gene that produces insulin is identified, restriction enzymes cut the human insulin making gene from the rest of the DNA, the plasmid is removed from the bacterium and cut open by the restriction enzymes, the insulin making genes are replaced with the plasmids (with sticky ends to join it back), joined by the ligase, the new plasmid is called the recombinant plasmid which is inserted back into the bacterium which now has a gene code for insulin, the bacteria multiplies rapidly inside an industrial fermenter.