Purestock/Purestock/Getty Images
Nucleic acids are the foundational biomolecules of life, encompassing deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA stores the genetic instructions that define an organism, while RNA interprets those instructions to synthesize proteins. Both polymers are built from units called nucleotides, though their sugar and base compositions differ slightly.
Both DNA and RNA feature a repeating backbone composed of alternating sugar and phosphate groups. The sugar in DNA is deoxyribose, lacking an oxygen at the 2' carbon, whereas RNA’s sugar, ribose, contains an extra hydroxyl group. This structural nuance confers distinct chemical stabilities to each molecule.
In DNA, two complementary strands coil into a right‑handed double helix, with nitrogenous bases pairing to form the ladder’s rungs. RNA, typically single‑stranded, adopts a variety of three‑dimensional shapes that facilitate its rapid interaction with proteins and other cellular components.
A nucleotide comprises a five‑carbon sugar, a phosphate group, and a nitrogenous base. The bases common to both DNA and RNA are adenine (A), guanine (G), and cytosine (C). The fourth base diverges: DNA uses thymine (T), whereas RNA substitutes uracil (U).
Both nucleic acids share the same elemental makeup: carbon, hydrogen, oxygen, nitrogen, and phosphorus. The sugars and bases are rich in carbon and hydrogen, with additional oxygen atoms in the sugars. Phosphate linkages contribute phosphorus and oxygen, while the bases incorporate both nitrogen and oxygen alongside carbon.
Deoxyribose’s lack of a 2' hydroxyl group renders DNA more chemically robust, safeguarding the long‑term integrity of genetic information. RNA’s ribose and single‑stranded nature make it less stable but highly adaptable, enabling swift synthesis and degradation as cells translate genetic codes into functional proteins.
