A – DNA
- Much wider and flatter.
- Right handed helix.
- major grooves: Narrow and deep
- minor grooves: wide and shallow
- Glycosidic bonds – anti-form
- 11 base pair
B – DNA
- Solid central core.
- Right handed
- Major groove: wide and narrow
- Minor groove: narrow and deep
- Glycosidic bond – anti-form
- 10 base pair
Z – DNA
- Solid core at centre.
- Left handed
- Major groove: More or less flat
- Minor groove: narrow and deep
- Glycosidic bond is anti-for Pyrimidines and syn-for Purines
- 12 base pairs

Parameter | A-DNA | B-DNA | Z-DNA |
Helix sense | Right | Right | Left |
Base pairs per turn | 11 | 10 | 12 |
Axial rise | 0.26 | 0.34 | 0.45 |
Helix pitch | 28 | 34 | 4.5 |
Base pair tilt | 20 | -6 | 7 |
Twist angle | 33 | 36 | -30 |
Diameter of helix | 2.3 | 2.0 | 1.8 |
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