In the model of DNA double helix structure proposed by Watson and Crick in 1953, two polynucleotide chains are wound in reverse parallel to each other to form a double helix with a diameter of 2nm; Complementary base pairs A-T and G-C are located in the helix through hydrogen bonds, and their planes are perpendicular to the helix axis, and the distance between two adjacent planes is 0.34nm. Every 10 base pair forms a complete right helix structure.

Extended data:

The significance of the double helix model is not only that the structure of DNA molecules has been proved, but more importantly, it also suggests the replication mechanism of DNA: since adenine (a) is always paired with thymine (t) and ornithine (g) is always paired with cytosine (c), it shows that the base sequences of the two chains are complementary, as long as the base sequence of one chain is determined, the other is.

Therefore, only one chain can be used as a template to synthesize and copy the other chain. Crick insisted from the beginning that "the principle of DNA specific pairing will immediately remind people of the possible replication mechanism of genetic material" should be added to the published papers.

Baidu encyclopedia -DNA double helix structure

Baidu encyclopedia -DNA double helix