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Which of the following enzymes is primarily responsible for joining adjacent DNA fragments during the construction of recombinant plasmids?

easy MCQ 1 mark Class 12 · Biology · Biotechnology Principles and Processes
  1. Restriction endonuclease
  2. DNA ligase
  3. DNA polymerase I
  4. Helicase
Answer
DNA ligase

The correct answer is DNA ligase — DNA ligase catalyses the formation of phosphodiester bonds between adjacent nucleotides, completing the recombinant plasmid; therefore option B is correct.

Step-by-step solution

  1. Identify the function required: joining two DNA fragments by forming phosphodiester bonds.
  2. Restriction endonucleases cut DNA; they do not join fragments, so option A is incorrect.
  3. DNA polymerase I fills gaps but does not ligate blunt or sticky ends, so option C is incorrect.
  4. Helicase unwinds DNA during replication; it does not ligate, so option D is incorrect.
  5. DNA ligase catalyses the formation of phosphodiester bonds between adjacent nucleotides, completing the recombinant plasmid; therefore option B is correct.
Common mistake: Choosing restriction enzyme instead of ligase

Concept tested: Role of DNA ligase

Published · How this solution was prepared and checked

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