Build a DNA Molecule

The structure of DNA is a double helix, much like a ladder that is twisted into a spiral shape. The bases of the DNA are found in pairs, which make up the rungs of the ladder. The uprights of the ladder are the structural backbone of the DNA. They don't carry information, they just hold the bases in their proper order.

DNA bases characteristically pair G with C, and A with T.

Use these pairing rules and the nucleotides below to build a DNA strand containing five base pairs.

Click and drag each nucleotide into position.

Funding provided by a Howard Hughes Medical Institute Precollege Science Education Initiative for Biomedical Research Institutions Award (Grants 51000125, 51000176)

Making Copies

When DNA is copied, the rungs of the ladder break right down the middle, and the uprights pull apart.

New bases are matched to the exposed bases on each upright, and the original DNA molecule becomes two new identical DNA molecules.

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