Drag it. Spin it. Take it apart.
Rotate the full double helix, zoom down to the individual hydrogen bonds, and click any rung to meet the base pair holding it together. Then flip to the nucleotide view to see what each rung is actually made of.
STRAND A · READS 5′ → 3′
STRAND B · READS 3′ → 5′ (ANTIPARALLEL)
ADENINE — PURINE · PAIRS WITH T · 2 H-BONDS
Four letters, two rules.
Adenine always reaches for thymine, guanine always for cytosine — a big double-ring purine locking onto a small single-ring pyrimidine, so every rung is exactly the same width. Tap a row to open that base in the nucleotide view.
Four moves and you've read the molecule.
Everything runs locally in your browser — nothing to install, nothing uploaded, nothing stored.
Pick your view
Start in the double helix for the whole molecule, then flip to the nucleotide view to take a single building block apart — phosphate, sugar and base.
Spin, drag & zoom
The helix turns on its own — grab it to steer, tilt by dragging up and down, and zoom until the hydrogen bonds between the bases come into view.
Click any rung
Every base pair opens a dossier: the two bases, how many bonds glue them together, and a quick fact. Tap the rails or the 5′ and 3′ tags to learn those too.
Read the sequence
Follow the letters along both strands under the helix — one runs 5′→3′, its partner runs the opposite way. Then hide the labels and quiz yourself.
DNA, measured.
The double helix is the most precisely specified molecule in biology — these are the numbers it keeps to.
The B-DNA spec sheet
B-DNA, the ordinary form of DNA, is two nanometres wide and completes a full twist every 3.4 nanometres — roughly ten and a half base pairs per turn. Every rung is the same length because every pair is purine + pyrimidine.
Your genome in numbers
Uncoil the 46 chromosomes packed into one of your cells and you'd carry off about two metres of DNA. Do it for every cell in your body and the ribbon would leave the solar system.
Chargaff's rules
In every species ever measured, adenine counts equal thymine counts and guanine equals cytosine. Erwin Chargaff found this in the 1940s — the clue that told Watson and Crick the bases simply had to pair up.
Things people ask.
Everything about how the model behaves, how honest the drawing is, and what it saves (nothing).
Still stuck? Write to us — we read everything.
How do I use the interactive DNA model?+
Drag anywhere on the model to rotate the double helix, scroll or pinch to zoom, and drag up or down to tilt it. Tap any rung to open its base pair, tap the rails for the backbone, or flip to the nucleotide view to take a single building block apart.
Is this DNA model to scale or scientifically exact?+
No. It's a stylized, idealized take on B-DNA — the ordinary form of DNA — built so every part is easy to see, click and tell apart. Real DNA bends, kinks, supercoils and is far more crowded than any diagram can show.
How do the four bases pair up?+
Adenine always pairs with thymine through two hydrogen bonds, and guanine always pairs with cytosine through three. Each pair joins one big double-ring purine to one small single-ring pyrimidine, which keeps the helix exactly the same width all the way along.
What's the difference between the helix view and the nucleotide view?+
The helix view shows the whole molecule — two strands and 24 base pairs you can rotate and zoom. The nucleotide view zooms right in on one building block, showing the phosphate, the deoxyribose sugar and whichever base you pick.
Why are the two strands called antiparallel?+
Because they run in opposite directions: read one strand 5'→3' and the strand across from it runs 3'→5', like two lanes of traffic facing opposite ways. The 5' and 3' tags on the sequence readout mark those ends.
What does the spin toggle do?+
It keeps the helix slowly turning on its own so it reads as a living 3D object rather than a flat picture. Grab it at any time to steer it yourself — the spin politely waits while you're inspecting.
Does the tool save or upload anything?+
No. The model runs entirely in your browser. Nothing you click, rotate, or select is ever sent to a server, logged, or stored.
Can I use this on my phone or tablet?+
Yes. One finger rotates and tilts, pinching zooms, and tapping selects — so the whole model works the same with touch as it does with a mouse.
Is this interactive DNA model free to use?+
Yes, it's completely free with no account, no sign-up, and no limit on how much you explore.