3D DNA Structure Viewer

Input any DNA sequence — select A, B, or Z-DNA — visualize the 3D helix structure in real time.

Sequence Input

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Bases
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GC
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Turns
B-DNA Physiological
A-DNA Dehydrated
Z-DNA Left-handed
Drag to rotate · Scroll to zoom · Right-click to pan · Click atoms to measure distance
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Understanding DNA Helix Structures

DNA exists in three major conformations depending on the environmental conditions. The 3D viewer above generates real coordinates using standard helix parameters from Saenger (1984), allowing you to visualize the differences between A-DNA, B-DNA, and Z-DNA directly in your browser.

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B-DNA (Physiological)
The most common form found in living cells. Right-handed helix with 10.5 base pairs per turn, 3.4 Å rise per bp, and 10.0 Å radius. Features asymmetric major and minor grooves.
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A-DNA (Dehydrated)
Found under dehydrated conditions. Wider (11.5 Å radius) with 11 bp per turn and 2.6 Å rise. The major groove is deep and narrow; the minor groove is wide and shallow.
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Z-DNA (Left-Handed)
A left-handed helix that forms in GC-rich regions under high salt conditions. Narrower (9.0 Å) with 12 bp per turn. Associated with gene regulation and chromatin remodeling.

The double helix is held together by hydrogen bonds between complementary base pairs: A pairs with T through two hydrogen bonds, while G pairs with C through three. The aromatic bases stack vertically through pi-pi interactions, stabilizing the helix interior. The major groove (wider) is where most DNA-binding proteins read the sequence, while the minor groove (narrower) is targeted by small-molecule binders.

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