Which term describes the monomer of nucleic acids made up of a five-carbon sugar, a phosphate group, and a nitrogenous base?

• A. Nucleotide
• B. Nucleosome
• C. Nucleoid
• D. Nitrogenous base

Answer: (A)

The building block of nucleic acids is a nucleotide, which is made up of three parts: a five-carbon sugar (deoxyribose in DNA or ribose in RNA), a phosphate group, and a nitrogenous base. This trio together forms the monomer that links together to create DNA and RNA strands through phosphodiester bonds, giving the backbone its structure while the bases pair to store and transmit genetic information. The other terms refer to different things: a nucleosome is DNA wrapped around histone proteins in chromosomes; a nucleoid is the region in prokaryotic cells where their DNA is located; a nitrogenous base is only the base component, not the full monomer. So the monomer described is the nucleotide.