Plastic model of the DNA molecule 20 000 000:1

The colored model of one turn of a double spiral DNA molecule made to order on the basis of X-ray crystallography data. Scale 20 000 000:1. In a living cell the majority of DNA molecules exist in B form. At this state the bases cyrcles are nearly perpendicular to the helical axis, and each base pair is twisted 36 degrees relative to the adjacent bases. Each complete turn of the molecule encompasses 3.4 nm that is 10 base pairs (9.7 and 10.6 in different crystals).