Insulin is a hormone produced by the pancreas which is a large gland present near the stomach. This hormone is necessary for the body’s correct use of food, especially sugar.
Insulin works by helping the sugar that penetrates the cell wall, where it is then utilized by the cell. In diabetic persons, the body either does not make enough insulin or the insulin that is produced cannot be used properly.
There are actually two forms of diabetes: type 1 (insulin- dependent) and type 2 (non-insulin-dependent). Type 1 usually requires insulin injection for life, while type 2 diabetes can usually be treated by dietary changes and/or oral antidiabetic medications.
Occasionally, type 2 diabetics must take insulin injections on a temporary basis, especially during stressful periods or times of illness.
There are different types of insulin that differ in several ways such as in the source (animal, human, or genetically engineered), in the time requirements for the insulin to take effect, and in the length of time the insulin remains working. Regular insulin is manufactured from beef and pork pancreas.
After introduction, it begins working within 30 to 60 minutes, and lasts for 6 to 8 hours. Moreover, variations of insulin have been developed to satisfy the needs of individual patients. Structure of insulin monomer is given in.
Animal-based insulin is a very safe product. However, some components may cause an allergic reaction. Therefore, genetically engineered human insulin has been developed to lessen the chance of an allergic reaction. It is structurally identical to the insulin produced by your body’s pancreas.
Transfer and Cloning of the Insulin Gene :
Insulin gene is transferred into a bacterial cell (E. coli) in the following two steps:
1. Transfer of the Insulin Gene into a Plasmid Vector:
The plasmid is cut across both strands by a restriction enzyme leaving the loose, sticky ends to which DNA can be attached. Special linking sequences (called linkers) are added to the human cDNA (complementary DNA) so that it will fit precisely into the loose ends of the opened ring of plasmid DNA.
The plasmid containing the human gene, also called a recombinant plasmid, is now ready to be inserted into another organism such as a bacterial cell (E. coli).
2. Cloning the Insulin Gene:
The recombinant plasmids and the bacterial cells are mixed up. Plasmid enters the bacterial cell through a process called transfection. The plasmid containing the human cDNA present inside bacterial cells is multiplied to get several dozen copies. When the bacteria divide, the plasmids also divide.
Thus two daughter cells and the plasmids continue to reproduce. With cells dividing rapidly (every 20 minutes), a bacterium containing human cDNA (encoding for insulin) will shortly produce many millions of similar cells called clones containing the same human gene.