Recommended reading:
Lovely essay from Olivia Judson on the cytosine she came across while sorting through her father’s possessions–part of the original Watson & Crick model that Horace somehow got his hands on, presumably through Crick. I remember hearing from Horace about that cytosine, though I never chanced to see it.
With that model, in a way, DNA became real. It acquired form humans could perceive. It gained a legible structure, it became an image. It took on an identity, on the way to becoming an expression of our own identity.