Deoxyribonucleic acid ( DNA ) is a molecule that cairies the genetic instructions uised in the growthe, development, functionin an reproduction o aw kent livin organisms an mony viruses . DNA an RNA are nucleic acids ; alongside proteins , lipids an complex carbohydrates ( polysaccharides ), thay are ane o the fower major types o macromolecules that are essential for aw kent forms o life . Maist DNA molecules conseest o twa biopolymer strands coiled aroond ilk ither tae form a dooble helix .

The twa DNA strands are termed polynucleotides syne thay are componed o simpler monomer units cried nucleotides . ^{[1] [2]} Ilk nucleotide is componed o ane o fower nitrogen-conteenin nucleobases ? cytosine (C), guanine (G), adenine (A), or thymine (T) ? a succar cried deoxyribose , an a phosphate group . The nucleotides are joined tae ane anither in a cheen bi covalent bonds atween the succar o ane nucleotide an the phosphate o the next, resultin in an alternatin succar-phosphate backbane . The nitrogenous bases o the twa separate polynucleotide strands are boond thegither, accordin tae base pairin rules (A wi T, an C wi G), wi hydrogen bonds tae mak dooble-strandit DNA. The tot amount o relatit DNA base pairs on Yird is estimatit at 5.0 x 10 ³⁷ an wechts 50 billion tonnes . ^[3] In comparison the tot mass o the biosphere haes been estimatit tae be as much as 4 trillion tons o carbon (TtC). ^[4]

DNA stores biological information . The DNA backbone is resistant tae cleavage, an baith strands o the dooble-strandit structur store the same biological information. This information is replicated as an when the twa strands separate. A lairge pairt o DNA (mair nor 98% for humans) is non-codin , meanin that thir sections dae nae serve as patterns for protein sequences.

The twa strands o DNA run in opposite directions tae ilk ither an are thus antiparallel . Attached tae each succar is ane o fower types o nucleobases (informally, bases ). It is the sequence o thir fower nucleobases alang the backbone that encodes biological information. RNA strands are creatit uisin DNA strands as a template in a process cried transcription . Unner the genetic code , thir RNA strands are translated tae specify the sequence o amino acids within proteins in a process cried translation .

Within eukaryotic cells DNA is organised intae lang structures cried chromosomes . In cell diveesion thir chromosomes are duplicated in the process o DNA replication , providin each cell its ain complete set o chromosomes. Eukaryotic organisms ( ainimals , plants , fungi , an protists ) store maist o thair DNA inside the cell nucleus an some o thair DNA in organelles , sic as mitochondria or chloroplasts . ^[5] In contrast prokaryotes ( bacteria an archaea ) store thair DNA anly in the cytoplasm . Within the eukaryotic chromosomes, chromatin proteins sic as histones compact an organise DNA. Thir compact structures guide the interactions atween DNA an ither proteins, helpin control which pairts o the DNA are transcribed.

DNA wis first isolated bi Friedrich Miescher in 1869. Its molecular structur wis identified bi James Watson an Francis Crick in 1953, whase model-biggin efforts war guidit bi X-ray diffraction data acquired bi Raymond Gosling , wha wis a post-graduate student o Rosalind Franklin . DNA is uised bi researchers as a molecular tuil tae explore physical laws an theories, sic as the ergodic theorem an the theory o elasticity . The unique material properties o DNA hae made it an attractive molecule for material scientists an engineers interested in micro- an nano-fabrication. Amang notable advances in this field are DNA origami an DNA-based hybrid materials. ^[6]

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