Schrödinger's code-script: not a genetic cipher but a code of development.

In his book What is Life? Erwin Schrödinger coined the term 'code-script', thought by some to be the first published suggestion of a hereditary code and perhaps a forerunner of the genetic code. The etymology of 'code' suggests three meanings relevant to 'code-script which we distinguish as 'cipher-code', 'word-code' and 'rule-code'. Cipher-codes and word-codes entail translation of one set of characters into another. The genetic code comprises not one but two cipher-codes: the first is the DNA 'base-pairing cipher'; the second is the 'nucleotide-amino-acid cipher', which involves the translation of DNA base sequences into amino-acid sequences. We suggest that Schrödinger's code-script is a form of 'rule-code', a set of rules that, like the 'highway code' or 'penal code', requires no translation of a message. Schrödinger first relates his code-script to chromosomal genes made of protein. Ignorant of its properties, however, he later abandons 'protein' and adopts in its place a hypothetical, isomeric 'aperiodic solid' whose atoms he imagines rearranged in countless different conformations, which together are responsible for the patterns of ontogenetic development. In an attempt to explain the large number of combinations required, Schrödinger referred to the Morse code (a cipher) but in doing so unwittingly misled readers into believing that he intended a cipher-code resembling the genetic code. We argue that the modern equivalent of Schrödinger's code-script is a rule-code of organismal development based largely on the synthesis, folding, properties and interactions of numerous proteins, each performing a specific task.