DNA by Francis Crick

Mention DNA today and immediately the iconic image of the double helix is conjured up - the familiar twisted ladder that carries the codes for the earth's huge variety of life forms. It wasn't always this way.

This view of DNA only goes back to the inspired homemade metal model created by Francis Crick and James Watson back in 1953. Determined to solve the puzzle posed by the research evidence at the time, they required new insight - insight that was finally achieved by visualising the structure through a physical model.

This pencil sketch of DNA was made by Francis Crick around this time and forms part of the extensive Crick archive. It illustrates several structural features of the double helix: the fact that it is right-handed with the two strands running in opposite directions; the fact that the nucleotides, the building blocks of the strands, have a part that forms the backbone and a part (the base) that projects into the middle of the helix; and the fact that the internally projecting bases in one strand are aligned so they can pair with one from the opposite strand.  This last feature is essential for DNA to be able to function in passing on the genetic information from generation to generation.

We can now only speculate as to whether this illustration came before or after the famous model, but it demonstrates the importance of simple illustrations in conceptualising and communicating complex problems.