Correct option is D
Explanation-
Correct statements-
Statement B - DNA strand separation by helicase
Helicase enzymes unwind the DNA double helix at the replication fork by breaking hydrogen bonds between base pairs. This process requires ATP hydrolysis for the helicase to translocate along the DNA strand.
Statement D - Joining of Okazaki fragments
DNA ligase seals the nicks between Okazaki fragments on the lagging strand. In eukaryotes, this enzyme uses ATP as a cofactor to form the phosphodiester bond during ligation.
Incorrect Statements-
Statement A - Phosphodiester bond formation
Though energy is used to form the phosphodiester bond, it comes from the dNTPs themselves, not from ATP hydrolysis. DNA polymerase uses the high-energy phosphate bonds of dATP, dGTP, dCTP, and dTTP.
Statement C - Clamp-loader association with clamp and DNA
False in eukaryotes, may not be as ATP-dependent as in prokaryotes
Although in prokaryotes, the clamp loader uses ATP to load the sliding clamp (β-clamp), in eukaryotes, the process is more complex and may not require ATP hydrolysis as directly or universally.
Thus, this may be considered non-essential ATP use in this context.
Final Answer - Only B and D are correct → Option d
