Which of the following statements is incorrect?

The correct answer is Option (4) → None of the above

Before human insulin was made by recombinant DNA technology, diabetics were given insulin from animals. All three statements describe insulin correctly, so none of them is incorrect.

Option (1) Insulin used for diabetes was earlier extracted from the pancreas of slaughtered cattle and pigs. — A correct statement. Insulin was earlier extracted from the pancreas of slaughtered cattle and pigs.

Option (2) Insulin from an animal source caused some patients to develop allergy or other types of reactions to the foreign protein. — A correct statement. Animal insulin is a foreign protein for the human body, and in some patients it caused allergy or other reactions.

Option (3) Insulin consists of two short polypeptide chains, chain A and chain B, which are linked together by disulphide bridges. — A correct statement. Insulin has two short chains, A and B, held together by disulphide bridges.

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).”

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