Question

The DNA replication starts
A. The leading strand produces Okazaki fragments.
B. The hydrogen bond between the nucleotide of the strands breaks.
C. The phosphodiester bonds between the adjacent nucleotides break.
D. The bond between the nitrogen base and deoxyribose sugar breaks.

Answer 1

Hint: Replication of the DNA happens in three elaborate steps. First is the opening of the double helical structure with separation of two strands of DNA. Second is the priming of the template strand by DNA primer, and last is the formation of the new DNA fragments. In separation steps, the two DNA strands unwind themselves at different locations called the origin.

Complete answer:
Initiation of DNA replication is done with the unwinding of the double helixes of DNA that are stuck together with the help of hydrogen bonds. Helicases is the enzyme that is responsible for breaking of the hydrogen bonds present between the nucleotide bases and thus, separate the two strands of the DNA. ATP hydrolase helps in providing the energy needed for this breakdown process of hydrogen bonds.

Option A is incorrect because Okazaki fragments are short sequences of DNA nucleotides (approximately to base pairs long in eukaryotes) which are synthesized discontinuously and later linked together by the enzyme DNA ligase to create the lagging strand during DNA replication. And Okazaki formation

Option C is incorrect because DNA polymerase is the enzyme that adds nucleotides to DNA primer by forming phosphodiester bonds in the backbone structure of the DNA. Thus, there is no breaking of the phosphodiester bonds between the adjacent nucleotides.

Option D is also incorrect because in the physiological process of metabolism, catabolism of nucleotides is responsible for the breaking of bonds between nitrogen bases and deoxyribose sugar.

Hence, the correct answer is option (B).

Note:The first step of the DNA replication starts with the unzipping of the DNA i.e. the breaking of the hydrogen bonds present between them. DNA helicases enzymes are essential to separate the DNA strands.
Polymerase enzymes perform the function of forming the hydrogen bond again in the latter steps of DNA replication.