Biology · Biotechnology and Its Applications · NEET
E. coli did NOT make ready-made insulin. Eli Lilly put two separate DNA sequences — one for chain A and one for chain B — into plasmids of E. coli. The bacteria produced chain A and chain B separately. The chains were then extracted and joined outside by making disulphide bonds. This two-chains-first step is what NEET tests most.
The main challenge was assembling insulin into a mature form. In the body, insulin is first made as proinsulin with an extra C-peptide that must be cut out. To skip this processing, Eli Lilly directly made only chain A and chain B in E. coli and joined them by disulphide bonds. So the rDNA product needs no C-peptide removal.
No. The C-peptide belongs to proinsulin (the pro-hormone) in the human body and is removed during maturation. Recombinant insulin from E. coli is built straight from separate A and B chains, so it never has a C-peptide. This is a very common NEET trap.
By disulphide bridges (–S–S– covalent bonds) between cysteine residues, NOT by hydrogen bonds. After E. coli makes the two chains, they are combined by creating these disulphide bonds to form functional human insulin.
Because the genetic code is nearly universal — the same codons code for the same amino acids in humans and in E. coli. So a human DNA sequence is translated correctly inside the bacterium, giving authentic human insulin chains.
Earlier, insulin was extracted from the pancreas of slaughtered cattle and pigs. This animal insulin sometimes caused allergy or immune reactions to the foreign protein. rDNA human insulin (Humulin) matches the human hormone, so it avoids these reactions and can be made in large amounts.
Which of the following genetically engineered organisms was used by Eli Lilly to prepare human insulin?
Which statement(s) is/are correct about genetically engineered Insulin? (a) Pro-hormone insulin contains extra stretch of C-peptide (b) A-peptide and B-peptide chains of insulin were produced separately in E. coli, extracted and combined by creating a disulphide bond between them (c) Insulin used for treating Diabetes was extracted from Cattle and Pigs (d) Pro-hormone insulin needs to be processed for converting into a mature and functional hormone (e) Some patients develop allergic reactions to the foreign insulin
Which of the following features of genetic code does allow bacteria to produce human insulin by recombinant DNA technology?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
In 1983, by Eli Lilly, an American company. They prepared DNA sequences for chains A and B of human insulin and expressed them in E. coli.
The main challenge was getting insulin assembled into a mature form. Eli Lilly solved this by making chain A and chain B separately in E. coli and then joining them by disulphide bonds, avoiding the need to process proinsulin.
Yes. The genetically engineered human insulin produced this way is marketed as Humulin. It matches human insulin, so it avoids the immune reactions caused by cattle and pig insulin.
Two — chain A and chain B — linked by disulphide bridges. The C-peptide of proinsulin is removed, so mature insulin never has three chains.
