DNA ligase

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DNA ligase is an enzyme that anneals DNA strands together. It forms a phosphodiester bond between the complementary bases on two separate DNA strands. ATP is hydrolysed in order to release a pyrophosphate, and the AMP that is formed attaches to the 5' end. The pyrophosphate bond activates the 5' end and a phosphodiester bond forms between the 5' phosphate and the 3' hydroxyl. DNA ligase is a crucial element in recombinant technology[1].

DNA ligase is an enzyme used for the ligation of blunt-ended and sticky ended recombinant fragments or Okazaki fragments. It works by repairing breaks in the sugar phosphate backbone in DNA by creating a covalent bond between adjoining nucleotides (between the 3’hydroxyl group of one DNA molecule with the 5’phosphoryl group of another)[2]. In eukaryotes DNA ligase I family members play the major role. The enzyme has a fundamental role in genetic engineering such as recombinant plasmid formation or Polymerase Chain Reaction[3].


  1. Alberts, Bruce. Molecular Biology of the Cell. 5th ed. New York: Garland Science, 2008, p 273
  2. Hartl D. L., Ruvolo M. (2012), Genetics: Analysis of genes and genomes, Eight Edition, Jones and Bartlett learning (Chapter 2 DNA Structure and Genetic Variation) p440-42
  3. Berg, J.M., Tymoczko, J.L. and Stryer, L. (2012). Biochemistry, 7 th Edition, New York, W.H.Freeman and Co Ltd. p152-153
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