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DNA is a double helix polymer of two antiparallel polynucleotide strands whose nucleotides form a sugar–phosphate backbone and whose bases pair via hydrogen bonds (A–T, C–G).
DNA is a double helix polymer made of two intertwined polynucleotide chains that carry genetic instructions for living organisms and many viruses. Each chain is built from repeating nucleotides, and each nucleotide contains a deoxyribose sugar, a phosphate group, and one of four nitrogen-containing bases: adenine (A), thymine (T), cytosine (C), or guanine (G). The sugar and phosphate form an alternating backbone via phosphodiester linkages, while the bases project inward and pair across the helix using hydrogen bonds according to Watson–Crick rules (A with T, and C with G). Because the strands are complementary, both strands store the same information, and separating them enables replication. The two DNA strands run in opposite directions (antiparallel), with each strand having distinct 5′ and 3′ ends that confer directionality. The double helix is primarily stabilized by hydrogen bonding between paired bases and by base-stacking interactions between neighboring aromatic bases. DNA’s structure also includes major and minor grooves, which provide accessible binding sites for proteins that recognize specific DNA sequences. In cells, DNA is further organized into chromosomes (in eukaryotes) or circular chromosomes (in prokaryotes), and it can be compacted by proteins such as histones, while processes like transcription and replication depend on the double helix being locally unwound and separated.
DNA is a double helix polymer of two antiparallel polynucleotide strands whose nucleotides form a sugar–phosphate backbone and whose bases pair via hydrogen bonds (A–T, C–G).
Genetic information is encoded in the sequence of bases along the backbone; strand complementarity allows replication and supports transcription into RNA.
The double helix’s stability comes mainly from hydrogen bonding and base-stacking, and its major/minor grooves help proteins bind specific DNA sequences.
The twisted, ladder-like structure formed when two DNA polynucleotide strands coil around each other.
A DNA building block consisting of deoxyribose sugar, a phosphate group, and one of four bases (A, T, C, or G).
The covalent bond between the sugar of one nucleotide and the phosphate of the next that forms the DNA backbone.
The arrangement where the two DNA strands run in opposite 5′→3′ directions.
Complementary hydrogen-bond pairing of A with T and C with G across the two DNA strands.
Unequally sized grooves formed by the geometry of the double helix that provide protein binding sites, with the major groove being wider.
Noncovalent interactions between adjacent bases that help stabilize the DNA double helix.
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