James Watson and Francis Crick discovered the structure of DNA at the Cavendish Laboratory in Cambridge. They knew that DNA is made up of four chemical compounds known as bases: adenine (A), thymine (T), guanine (G) and cytosine (C). They also discovered the structure of DNA by figuring out how the four DNA bases fit together, just like putting together the pieces of a jigsaw puzzle.

DNA bases always form the same pairs: A-T and G-C. In human bodies, the proportion of A-T and G-C bases is about 3:2. In this flash simulation, there are 3 pairs of A-T bases and 2 bases of G-C bases, representing the proportion of A-T and G-C bases in human bodies.

Target: Try to match A-T and G-C bases in the interactive DNA jigsaw. You can rotate each base by pressing Alt-click (Windows) or Option-click (Macintosh).

You need Flash 6 + IE 5.5 and above to play with the interactive DNA jigsaw.

A printable version of the DNA jigsaw forms part of the Making Models of DNA resource.