In the letter, Crick sketches what is now perhaps one of the most famous scientific diagrams in world—the structure of DNA.
19 Portugal Place Cambridge
19 March ’53
My Dear Michael,
Jim Watson and I have probably made a most important discovery. We have built a model for the structure of de-oxy-ribose-nucleic-acid (read it carefully) called D.N.A. for short. You may remember that the genes of the chromosomes — which carry the hereditary factors — are made up of protein and D.N.A.
Our structure is very beautiful. D.N.A. can be thought of roughly as a very long chain with flat bits sticking out. The flat bits are called the “bases”. The formula is rather like this.