Choose the correct statement about genetically engineered insulin.

The correct answer is Option (3) → Eli Lilly, an American company, prepared two DNA sequences corresponding to A and B, chains of human insulin.

Insulin for diabetics was once taken from animals, and it caused allergy in some patients. Human insulin is now made by recombinant DNA technology. Insulin has two short chains, A and B, joined by disulphide bridges.

Option (1) Insulin used for diabetes was earlier extracted from the pancreas of slaughtered mice and monkeys. — Incorrect. Insulin was earlier extracted from the pancreas of slaughtered cattle and pigs, not mice and monkeys.

Option (2) Insulin consists of two long polypeptide chains: chain A and chain B, that are linked together by hydrogen bridges. — Incorrect. The two chains of insulin are short, and they are linked by disulphide bridges, not hydrogen bridges.

Option (3) Eli Lilly, an American company, prepared two DNA sequences corresponding to A and B, chains of human insulin. — Correct. In 1983, Eli Lilly prepared two DNA sequences corresponding to chains A and B of human insulin. It put them into plasmids of E. coli, which made the two chains separately.

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 1983, Eli Lilly an American company prepared two DNA sequences corresponding to A and B, chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains.”

Figure 10.3 Maturation of pro-insulin into insulin (simplified)