During DNA replication the weak hydrogen bonds between nitrogenous bases of the nucleotide separate

by- Indra Bhan

So that the two polynucleotide chains of DNA  also separate and uncoil.

The chains thus separated are complimentary to one another.

Because of the specificity Of the base pairing, each nucleotide of separated chains attracts

its Complementary nucleotide from the cell cytoplasm.

Once the nucleotides are attached by their hydrogen bonds to sugar radicals unite through their phosphate components,

completing the formation of a new polynucleotide chain.

Thus each chain of the double helix of DNA serves as a template or model on which its complementary chain is built.

This method of DNA replication is described as a semi-conservative method ...