First, let's review. A nucleotide is any of a group of molecules that, when linked together, form the building blocks of DNA or RNA: composed of a phosphate group, the bases adenine, cytosine, guanine, and thymine, and a pentose sugar, in RNA the thymine base being replaced by uracil.
Another way:
Each nucleotide is a monomer made composed of a nitrogenous base, a pentose sugar, and a phosphate group that serves as the foundation for nucleic acids. In nucleotide polymers and nucleic acids, each specific sequence of nitrogenous bases corresponds to a distinct gene that can be thousands of nucleotides long.
There are two different kinds of nucleic acids: DNA (deoxyribonucleic acid), which consists of two complementary strands with their nitrogenous bases hydrogen bound together to form a double helix, and single-stranded RNA (ribonucleic acid), which has four subtypes.
Thank you,
Eddie