DNA by Francis Crick
Pencil sketch c1953
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 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.