A focus on new kinds of model organisms such as viruses and bacteria, along with the discovery of the double helical structure of DNA in 1953, marked the transition to the era of molecular genetics.

James Watson and Francis Crick determined the structure of DNA in 1953, using the X ray crystallography work of Rosalind Franklin and Maurice Wilkins that indicated DNA had a helical structure (i.e., shaped like a corkscrew).

But before doing that, I just briefly want to remind you about what you already know that our genomes, our genetic material, are stored in almost all cells in our bodies in chromosomes in the form of DNA, which is this famous double helical molecule.

And the reason for doing so, at the center of this photograph, is Linus Pauling. About six months before, he proposed the alpha helical structure for proteins. And in doing so, he banished the man out on the right, Sir Lawrence Bragg, who was the Cavendish professor.