Genetic engineering is the manipulation of genes. It is also called recombinant DNA technology. In genetic engineering, pieces of DNA (genes) are introduced into a host by means of a carrier (vector) system. The foreign DNA becomes a permanent feature of the host, being replicated and passed on to daughter cells along with the rest of its DNA. Bacterial cells are transformed and used in production of commercially important products. The examples are production of human insulin (used against diabetes), human growth hormone (somatotrophin used to treat pituitary dwarfism), and infections which can be used to help fight viral diseases. Insulin is a hormone that converts extra blood glucose to glucose.
It is produced by pancreas in the body. In people with deficiency of insulin, extra glucose is excreted in urine. This disease is called Diabetes mellitus. People suffering from it need to insulin every day.