Explain how the structure of a DNA nucleotide differs from that of an RNA nucleotide, and how these structural differences affect the chemical stability of each type of nucleic acid.

DNA nucleotides contain deoxyribose, which lacks the 2′‑hydroxyl group that ribose in RNA possesses. Consequently, DNA bases are adenine, guanine, cytosine and thymine, whereas RNA bases are adenine, guanine, cytosine and uracil. The absence of the 2′‑OH in DNA means the sugar is less reactive, and the phosphodiester backbone is less prone to intramolecular attack. In RNA the 2′‑OH can act as a nucleophile, attacking the adjacent phosphodiester bond and causing hydrolysis, especially under alkaline conditions. Thus RNA is chemically less stable than DNA. DNA’s greater stability, together with its double‑stranded helical structure, makes it ideal for long‑term storage of genetic information, whereas RNA’s relative instability is acceptable for its transient, functional roles.