Lesson eLearning

Briefly explain the specific function of DNA ligase in the construction of recombinant plasmids.

medium 2 marks Class 12 · Biology · Molecular Basis of Inheritance
Answer
DNA ligase joins the phosphate‑backbone of adjacent DNA fragments, sealing nicks to produce a continuous circular plasmid

Step-by-step solution

  1. State that recombinant DNA technology often involves cutting a vector and an insert with restriction enzymes.
  2. Point out that this creates complementary sticky or blunt ends but leaves a break in the sugar‑phosphate backbone.
  3. Explain that DNA ligase catalyzes the formation of phosphodiester bonds between the 3′‑OH and 5′‑phosphate of adjacent nucleotides.
  4. Conclude that this sealing step converts the linear ligated product into a stable circular recombinant plasmid.
Common mistake: Confusing the activity of DNA ligase with DNA polymerase’s synthesis of new strands

Concept tested: Role of DNA ligase in recombinant DNA

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