Identify the correct statements about insulin:(A) Insulin has two pol…

The correct answer is Option (4) → Only (B) and (C)

(A) Insulin has two polypeptide chains linked by phosphodiester bonds. — Incorrect. The two chains are linked by disulphide bridges. Phosphodiester bonds join the nucleotides of DNA and RNA.

(B) It is synthesised in the form of a pro-hormone and needs to be processed before becoming a fully functional hormone. — Correct. The pro-hormone becomes active insulin only after processing.

(C) Pro-hormone of insulin has an extra stretch called C peptide. — Correct. The C peptide is not present in mature insulin.

(D) An American company, Eli Lilly, prepared two RNA sequences of insulin. — Incorrect. In 1983 Eli Lilly prepared two DNA sequences, for chains A and B. They were put into plasmids of E. coli to make the insulin chains.

NCERT Extract:
Genetically Engineered Insulin – “… Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges (Figure 10.3). 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.”
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)