Starting material for the production of insulin from bacteria is -

Human insulin (Humulin) is produced from bacterial cells (E. coli) using 'Recombinant DNA' technology. Here a DNA segment containing a gene to be cloned is inserted into plasmid DNA of the bacterium. Plasmids are circular segments of DNA, which are independent of the chromosomes and capable of replication thus producing multiple copies. When the bacterial cell divides, the plasmids are split between the two daughter cells. These daughter cells then produce more plasmids which are then passed on to their daughter cells, etc. With cells dividing as fast as every 20 minutes, a bacterium containing human DNA encoding insulin will, in a relatively short time, produce many millions of similar cells (clones) containing the same human gene. These bacteria containing insulin gene are then grown under conditions that will lead to optimal insulin production. The insulin is then collected, isolated, and purified. The process begins with obtaining a human DNA containing the insulin gene. Isolation of a specific gene from the human DNA is a laborious process. It is thus easier to start the process by obtaining insulin mRNA from the beta cells of the pancreas where insulin is being produced in abundance. A complementary copy of DNA (cDNA) containing the insulin gene is then produced from the insulin mRNA using reverse transcriptase technology. This cDNA is then cloned by inserting into the plasmid vector.