what are the building blocks of dna?

The building blocks of DNA are nucleotides, which are the basic units that compose DNA strands. Each nucleotide consists of three parts: a phosphate group, a sugar molecule (deoxyribose in DNA), and a nitrogenous base. There are four types of bases in DNA: adenine (A), thymine (T), cytosine (C), and guanine (G). These nucleotides polymerize in long chains through phosphodiester bonds, forming the sugar–phosphate backbone with the bases extending to the inside, where A pairs with T and C pairs with G to create the double-helix structure.