Overview
Nucleic acids are long biological polymers responsible for storing and transmitting genetic information in living organisms. Two principal classes exist: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Together they determine the sequence of hereditary units and guide the production of proteins and functional RNAs. At a basic level nucleic acids are large molecular chains built from repeating units called nucleotides, a type of large biological macromolecule.
Composition and basic structure
Each nucleotide contains three parts: a nitrogenous base, a five-carbon sugar, and a phosphate group. Bases fall into two families: purines (adenine and guanine) and pyrimidines (cytosine, thymine in DNA, or uracil in RNA). Nucleotides link by phosphate–sugar backbones to form long strands. Complementary base pairing (A with T or U, and C with G) allows double-stranded DNA to form a stable double helix, while RNA is commonly single-stranded and more structurally diverse.
Cellular roles and processes
DNA acts principally as the long-term repository of genetic information and is commonly organized into chromosomes in the cell nucleus or in organelles such as mitochondria. During cell division DNA is copied so genetic information passes to daughter cells. The sequence of bases in DNA is transcribed into RNA, and certain RNA molecules—most notably messenger RNA—are then translated into proteins. Other RNAs perform structural or regulatory functions rather than encoding proteins; such molecules are often referred to as non-coding RNAs.
Major differences between DNA and RNA
- Sugar: DNA contains deoxyribose while RNA contains ribose, a difference of one oxygen atom that affects stability.
- Bases: DNA uses thymine (T); RNA substitutes uracil (U) for thymine.
- Strand form: DNA is usually double-stranded; RNA is usually single-stranded and can fold into complex shapes.
- Function: DNA primarily stores genetic information; RNA fulfills diverse roles in expression, catalysis and regulation.
History and scientific development
Recognition of nucleic acids as key biomolecules began with the isolation of a substance from cell nuclei in the late 1800s. In the 20th century researchers established the chemical components and the double-helix structure of DNA, which provided a physical basis for heredity and inspired modern molecular biology. Discoveries since then have revealed many forms and functions of RNA, expanding appreciation of nucleic acids beyond simple genetic storage.
Importance, applications, and notable facts
Nucleic acids are central to genetics, medicine and biotechnology. Techniques that read or edit DNA and RNA sequences underpin genetic testing, forensic identification, disease research, and many biotechnological products. Epigenetic chemical modifications of DNA and associated proteins influence gene activity without changing sequence. In addition, some viruses use RNA as their genetic material, and many organisms use extensive networks of non-coding RNAs to regulate genes.
Key processes summarized
- Replication — accurate copying of DNA for cell division.
- Transcription — synthesis of RNA from a DNA template (see transcription).
- Translation — decoding mRNA to build proteins (see translation).
For more detailed treatments of chemical structure and cellular mechanisms, follow introductory resources and reviews that explain nucleotide chemistry, chromosomal organization, and the expanding roles of non-coding RNAs in gene regulation. Additional background and specific examples are available through linked resources on structure and function (macromolecules, cellular compartments).