Logical sequence in recombinant insulin production

Steps:

• Insert the human insulin gene into E. coli DNA to create genetically modified bacteria (stage 2).
• Grow the modified E. coli in large fermenters to produce insulin (stage 1).
• Extract and purify the insulin from the bacteria (stage 3).
• Process the purified insulin for medical use (stage 4).

Why D is correct:

• D (2→1→3→4) matches the recombinant DNA technology process, where gene insertion precedes bacterial proliferation, extraction, and final preparation.

Why the others are wrong:

• A begins with extraction (3) before gene insertion (2), violating production logic.
• B reverses the order starting with final processing (4) before production.
• C inserts final processing (4) before extraction (3), disrupting the flow.

Final answer: D