DNA Structure

In-depth explanation of DNA Structure

DNA is a double helix made of two antiparallel polynucleotide strands. Each strand has a backbone of alternating deoxyribose sugar and phosphate groups, with the nitrogenous bases projecting inward and pairing across the helix. The base pairs are held together by hydrogen bonds, two between A and T and three between G and C, and the sequence of bases stores the genetic information. The helix is right-handed, with about 10 base pairs per turn and a pitch of about 3.4 nm. The Watson and Crick model of 1953 was built in part on X-ray diffraction data from Rosalind Franklin.

Going deeper: DNA Structure

Key ideas: Double helix of two antiparallel strands, each a chain of deoxyribose sugars linked by phosphodiester bonds (3 to 5 direction). B-DNA has 10.5 base pairs per turn, 3.4 angstrom rise per pair, 20 angstrom diameter, with major and minor grooves. Bases sit inside, phosphates outside, giving DNA a negative charge.

Common mistakes and connections: Students think the strands run in the same direction or that bases are on the outside. Hydrogen bonds hold strands together while covalent phosphodiester bonds make each backbone. Chargaff rule: A equals T and G equals C in double-stranded DNA. Links to base pairing, replication and electrophoresis.

Visualization of DNA Structure

The DNA double helix: two antiparallel strands with a sugar-phosphate backbone outside and base pairs inside, about 10 base pairs and 3.4 nm per turn. The interactive lesson shows this as a live animation or chart.

Worked example and use case

Replacing a G-C pair with an A-T pair changes the local stability of the helix.

Where DNA Structure fits in Biochemistry, Environment & Industry

DNA Structure is topic 23 of 127 in Biochemistry, Environment & Industry.

Related topics

• Trans FatsAdvanced
• PhospholipidsAdvanced
• CholesterolAdvanced
• RNA TypesIntermediate
• Base PairingIntermediate
• DNA ReplicationAdvanced

Browse all 127 topics in Biochemistry, Environment & Industry