DNA and RNA are made up of what building block?

Nucleotides are the monomers, building blocks, of nucleic acids (DNA and RNA). Each nucleotide includes three components: a phosphate, a sugar, and a nitrogenous base. The phosphate is bonded to the sugar through phosphodiester bonds and makes up the backbone of the molecule. The nitrogenous bases form the "rungs" of the ladder and are connected through hydrogen bonds. The phosphate is the same in DNA and RNA, but the sugar can be a ribose (for RNA) or a deoxyribose (for DNA). The latter is a ribose without "de-" one oxygen "-oxy-". There are four available nitrogenous bases in a DNA's nucleotides: adenine, thymine, guanine, and cytosine. RNA nucleotides feature the same bases with the exception of uracil, which replaces thymine.