Molecular building blocks of nucleic acids; consists of a phosphate, sugar, and base.

• A. Base
• B. Nucleotide
• C. Amino Acids
• D. Sugar

Answer: (B)

Nucleotides are the molecular building blocks of nucleic acids, and each nucleotide consists of a phosphate group, a five‑carbon sugar, and a nitrogenous base. This trio is the essential unit that polymerizes to form DNA and RNA; the sugar and phosphate create the backbone, while the base carries the genetic information. In DNA the sugar is deoxyribose and the bases are A, T, C, and G; in RNA the sugar is ribose and the bases are A, U, C, and G. Saying “base” or “sugar” alone describes parts of the molecule, but the complete, functional unit of nucleic acids is the nucleotide.