Genetically modified bacteria (recombinant bacteria) with the human gene for insulin is useful because after it’s being put in fermentation tank it starts to produce human insulin protein. The process of making recombinant bacteria includes DNA cloning.
A target gene, in this case, insulin gene, is inserted into a circular piece of DNA called a plasmid via restriction enzymes and DNA ligases. Recombinant DNA is then introduced into bacteria via a process called transformation. With the right conditions the bacteria that contains the human insulin gene, will start transcribing the gene and translating the mRNA to produce many molecules of human insulin protein.