Question

The role of DNA ligase in the construction of a recombinant DNA molecule is

• A. Formation of phosphodiester bond between two DNA fragments
• B. Formation of hydrogen bonds between sticky ends of DNA fragments
• C. Ligation of all purine and pyrimidine bases
• D. None of the above

Answer 1

Answer: (A)

Formation of phosphodiester bond between two DNA fragments

Answer 2

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.