His observations turned out to be closely connected to the finding of nuclein.
Mendel was able to show that certain traits in the peas, such as their shape or color, were inherited in different packages. For a long time the connection between nucleic acid and genes was not known.
The scientist Linus Pauling was eager to solve the mystery of the shape of DNA.
In 1954 he became a Nobel Laureate in Chemistry for his ground-breaking work on chemical bonds and the structure of molecules and crystals.
He called the compound "nuclein." This is today called nucleic acid, the "NA" in DNA (deoxyribo-nucleic-acid) and RNA (ribo-nucleic-acid).
Two years earlier, the Czech monk Gregor Mendel, had finished a series of experiments with peas.
This picture of DNA that had been crystallized under moist conditions shows a fuzzy X in the middle of the molecule, a pattern indicating a helical structure.
The base-pairing mystery had been partly solved by the biochemist Erwin Chargoff some years earlier.
But Watson did not take notes, and remembered the numbers incorrectly.
Instead, it was Franklin's famous "photograph 51" that finally revealed the helical structure of DNA to Watson and Crick in 1953.