What is the monomer unit of nucleic acids?

The monomer unit of nucleic acids is a nucleotide. Nucleotides are the building blocks that make up nucleic acids such as DNA and RNA. Each nucleotide consists of three components: a phosphate group, a five-carbon sugar (ribose in RNA and deoxyribose in DNA), and a nitrogenous base (which can be adenine, thymine, cytosine, or guanine in DNA, and adenine, uracil, cytosine, or guanine in RNA).

This structure allows nucleotides to link together through phosphodiester bonds, forming the long chains of nucleic acids that carry genetic information. The arrangement and sequence of these nucleotides encode the genetic instructions necessary for the development, functioning, and reproduction of all living organisms and many viruses. The other choices represent different types of biomolecules: amino acids are the monomers of proteins, fatty acids are components of lipids, and monosaccharides are the simplest units of carbohydrates. Therefore, nucleotides distinctly serve as the fundamental units that compose nucleic acids.