What is DNA?

Structure

DNA is a polymer of nucleotides, each comprising a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases — adenine (A), thymine (T), guanine (G), or cytosine (C). The sugar and phosphate groups form a backbone, while the bases project inward. Two such strands wind around each other as an antiparallel double helix, a structure described by James Watson and Francis Crick in 1953 using the X-ray crystallography of Rosalind Franklin and Maurice Wilkins. The strands are held together by hydrogen bonds between complementary bases: A always pairs with T, and G always pairs with C.

How it works

Because the two strands are complementary, each can serve as a template to build the other. During replication the helix unwinds and DNA polymerase synthesises a new partner strand for each original, so every daughter cell receives a faithful copy of the genome.

The base sequence is read in groups, and genes within the DNA are transcribed into RNA and, for protein-coding genes, translated into proteins. In this way the chemical order of A, T, G, and C is converted into the molecules that build and run a cell.

Significance in research

DNA is the basis of heredity, evolution, and modern molecular biology. Determining and comparing DNA sequences underpins genomics, forensic identification, phylogenetics, and the diagnosis of inherited conditions in research settings. Techniques such as the polymerase chain reaction (PCR) and DNA sequencing let researchers amplify and read DNA, while genome-editing tools such as CRISPR allow targeted changes to be studied. Standardised description of sequence data — through shared databases and metadata — is central to making genomic research findable and reusable.

History and standards

The chemical nucleic acid was first isolated by Friedrich Miescher in 1869, but its role as the hereditary material was confirmed only in the mid-twentieth century, notably by the Avery–MacLeod–McCarty experiment (1944) and the Hershey–Chase experiment (1952). The 1953 double-helix model unified the chemistry with the mechanism of heredity. Today, public sequence repositories such as GenBank and the European Nucleotide Archive curate DNA data under community standards, supporting reproducible, FAIR research.