What materials did Watson and Crick use to build their 1953 DNA model?

Watson and Crick used metal and cardboard to build their 1953 DNA model. Their model-building process combined sturdy metal components with cardboard cut-outs representing the molecule’s chemical parts.

The cardboard pieces were especially useful for experimenting with the four DNA bases: adenine, thymine, cytosine, and guanine. Watson could move the shapes around like a puzzle while testing how their chemical structures might fit together. Correctly pairing adenine with thymine and cytosine with guanine helped reveal how the two strands could be held together.

The finished model was a large, three-dimensional structure based on chemical bond lengths, known molecular geometry, Chargaff’s base-pairing observations, and X-ray diffraction evidence, including work by Rosalind Franklin and Raymond Gosling. The model represented DNA as a double helix with sugar-phosphate backbones on the outside and paired bases inside.

A common mix-up is remembering only the cardboard. Cardboard was used for trial pieces and base cut-outs, while the completed model prominently incorporated metal plates and other metal components.