The diagram shows a bacterial cell that is used in genetic modification.
Which labelled structure makes the bacterium useful for genetic modification?
▶️ Answer/Explanation
Ans: C
Plasmids (C) are small, circular DNA molecules in bacteria that can be easily modified to carry foreign genes. They replicate independently and are key tools in genetic engineering. The other structures (cell wall, flagellum, ribosome) don’t directly facilitate genetic modification.
The stages describe how genetic modification can be used to produce human insulin from bacteria.
- Cut bacterial plasmid DNA with restriction enzymes.
- Extract the gene for insulin from human DNA with restriction enzymes.
- Insert the recombinant plasmids into bacteria.
- Join human DNA to bacterial plasmid DNA using DNA ligase.
- Replicate bacteria containing recombinant plasmids.
Which sequence will lead to the production of human insulin by bacteria?
▶️ Answer/Explanation
Ans: A
The correct sequence for genetic modification to produce human insulin is:
- Cut plasmid DNA (Step 1)
- Extract insulin gene (Step 2)
- Join DNA using ligase (Step 4)
- Insert into bacteria (Step 3)
- Replicate bacteria (Step 5)
This matches sequence A (1 → 2 → 4 → 3 → 5) in the diagram.
Why this order? The plasmid must first be prepared (1), then the gene isolated (2), combined (4), inserted (3), and finally the bacteria grown (5) to produce insulin.