What term describes the shape of DNA?

The shape of DNA is a double helix: two complementary strands twisted around one another like a spiral ladder. The sugar-phosphate backbones form the sides, while paired bases form the rungs.

The best-known cellular form is B-DNA, a right-handed helix with roughly 10 to 10.5 base pairs per turn. Its two grooves are called the major groove and minor groove; many DNA-binding proteins recognise chemical patterns exposed in the wider major groove.

James Watson and Francis Crick published the double-helix model in 1953, drawing on crucial evidence from Rosalind Franklin and Raymond Gosling’s X-ray diffraction work, Maurice Wilkins’s research, and Erwin Chargaff’s base-pairing observations. The model explained both how DNA stores information and how its strands can serve as templates for copying.

DNA is not always geometrically identical. A-DNA and Z-DNA are other recognised conformations, and DNA can bend, supercoil, and pack tightly inside cells. These variations do not change the standard quiz answer: ordinary double-stranded DNA is described as a double helix.