: any of various nucleic acids that are usually the molecular basis of heredity, are constructed of a double helix held together by hydrogen bonds between purine and pyrimidine bases (see base entry 1 sense 6b) which project inward from two chains containing alternate links of deoxyribose and phosphate, and that in eukaryotes are localized chiefly in cell nuclei compare recombinant dna

Illustration of DNA

Illustration of dna
  • A molecular model
  • 1 hydrogen
  • 2 oxygen
  • 3 carbon in the helical phosphate ester chains
  • 4 carbon and nitrogen in the cross-linked purine and pyrimidine bases
  • 5 phosphorus
  • B double helix

Examples of DNA in a Sentence

Recent Examples on the Web
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But important clues about how the sickness operates are emerging from the latest studies of bacterial DNA in ancient bones and teeth. — Faye Flam, Scientific American, 27 Oct. 2026 Investigators swabbed the home for DNA, and in 2019 developed a profile that matched Pollard, court records show. — Grethel Aguila, Miami Herald, 26 Oct. 2026 In January, Sorrells created a cold case task force that is using advances in DNA technology to try to identify suspects in dormant homicide investigations. — Fort Worth Star-Telegram, 24 Oct. 2026 Three months later the McCanns were named suspects after Madeleine’s DNA was reportedly found in a car the couple had rented a few weeks after her disappearance. — Frannie Comstock, Encyclopedia Britannica, 23 Oct. 2026 See All Example Sentences for DNA

Word History

Etymology

deoxyribonucleic acid

First Known Use

1944, in the meaning defined above

Time Traveler
The first known use of DNA was in 1944

Browse Nearby Words

Cite this Entry

“DNA.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/DNA. Accessed 27 Oct. 2026.

Kids Definition

: any of various nucleic acids that are located especially in cell nuclei, are usually the chemical basis of heredity, and are composed of two nucleotide chains held together by hydrogen bonds in a pattern resembling a flexible twisted ladder compare rna

Medical Definition

: any of various nucleic acids that are usually the molecular basis of heredity, are constructed of a double helix held together by hydrogen bonds between purine and pyrimidine bases which project inward from two chains containing alternate links of deoxyribose and phosphate, and that in eukaryotes are localized chiefly in cell nuclei

called also deoxyribonucleic acid

see recombinant dna

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