The role of DNA ligase in the construction of a recombinant DNA molecule is:
a. Formation of a 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
The answer is option (a) Formation of a phosphodiester bond between two DNA fragments.
Explanation: DNA ligase facilitates the joining of two sticky ends of DNA fragments by the formation of a phosphodiester bond between them.