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Q.
The role of DNA ligase in the construction of a recombinant DNA molecule is
Biotechnology : Principles and Processes
Solution:
DNA ligases (joining or sealing enzymes) are also called genetic gum. They join two individual fragments of double stranded DNA by forming phosphodiester bonds between them. Thus, they help in sealing gaps in DNA fragments. Therefore, they act as a molecular glue. The enzyme used most often in the rDNA technology is $T_4$ DNA ligase.