The B-form DNA double helix

(a) Ribbon diagram, (b) space-filling diagram, and (c) balland- stick diagram show the sugar-phosphate backbones, base pairs, major and minor grooves, and dimensions of the DNA duplex(a) Ribbon diagram, (b) space-filling diagram, and (c) balland- stick diagram show the sugar-phosphate backbones, base pairs, major and minor grooves, and dimensions of the DNA duplex

(a) Ribbon diagram (b) Space-filling diagram (c) Ball-and-stick diagram Complementary Complementary Complementary Strand 1 base air ' ' 3’ P Strand 2 Stragnld ,1 base pair Strand 2 Stra3nd 1 base pa|r Strand 2 95’ Phosphate Axis of _ _ groups helical groups $315 nozthjlical symmetry Sugar G rings Minor Minor groove groove One helical 3'4 A 3.4 A turn = 34 A = 3.4 nm = 34 A 1025 base pairs Major Major groove groove 20 A (2 nm) 20 A 20 A