Assertion (A): The production of synthetic human insulin through recombinant DNA technology has provided a safer source of insulin for diabetes management.
Reason (R): During the maturation process into insulin, the C-peptide is removed, and it is not present in the mature insulin.
In light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Both A and R are true, but R is not the correct explanation of A.
Assertion (A): The production of synthetic human insulin through recombinant DNA technology has provided a safer source of insulin for diabetes management. — True. Insulin for diabetes was earlier taken from the pancreas of slaughtered cattle and pigs. This animal insulin caused allergy or other reactions to the foreign protein in some patients. Human insulin made by recombinant DNA technology (in E. coli, by Eli Lilly in 1983) avoids this, so it is a safer source.
Reason (R): During the maturation process into insulin, the C-peptide is removed, and it is not present in the mature insulin. — True. In humans, insulin is made as a pro-hormone (pro-insulin) with an extra stretch called the C peptide. The C peptide is removed during maturation, so mature insulin has only chains A and B joined by disulphide bridges.
Why R does not explain A? A is about the source of insulin: rDNA human insulin is safer because it is not a foreign animal protein. R is about how natural insulin matures in the body by losing its C peptide. The removal of the C peptide happens in all insulin and is not what makes rDNA insulin safer; in fact, the rDNA method made chains A and B separately and joined them. So both statements are correct, but R is not the explanation of A.
NCERT Extract:
Genetically Engineered Insulin – “… Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs. Insulin from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein. Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges (Figure 10.3).”
Genetically Engineered Insulin – “In mammals, including humans, insulin is synthesised as a pro-hormone (like a pro-enzyme, the pro-hormone also needs to be processed before it becomes a fully mature and functional hormone) which contains an extra stretch called the C peptide. This C peptide is not present in the mature insulin and is removed during maturation into insulin.”
Figure 10.3 Maturation of pro-insulin into insulin (simplified)