Write the structures of fragments produced on complete hydrolysis of DNA. How are they linked in DNA molecule? Draw a diagram to show pairing of nucleotide bases in double helix of DNA.

Explanation

On complete hydrolysis of DNA, following fragments are formed a pentose sugar `(beta-D-2` deoxyribose) phosphoric acid `(H_(3)PO_(4))` and bases (nitrogen containing heterocyclic compounds).

(iii) Nitrogen bases DNA contains four bases Adenine (A), Guanine (G), Cytosine (C) and thymine (T).

A unit formed by the attachment of a base to 1'-position of sugar is called nucleoside. when nucleoside links to phosphoric acid a 5'-position of sugar moiety, a nucleotide is formed. Nucleotides are joined together by phosphodiester linkage between 5' and 3' carbon atoms of the pentose sugar. In DNA two nucleic acid chains are wound about each other and held together by hydrogen bonds between pairs of bases.
The two strands are complementary to each other because hydrogen bonds are formed between specific pair of base adenine form hydrogen bonds with thymine whereas cytosine form hydrogen bonds with guanine.