Watson and Crick’s second paper of 1953, which discussed the genetical implications of their recently discovered (Watson and Crick 1953a) double-helical structure of DNA, used both “code” and “information”: .
In more detail, the transfer of information from nucleic acid to nucleic acid, or from nucleic acid to protein may be possible, but transfer from protein to protein, or from protein to nucleic acid is impossible.
Max Delbrueck also became interested in the physical basis of heredity after hearing a lecture by his teacher, quantum physicist Niels Bohr (1933), which expounded a principle of complementarity between physics and biology (Mc Kaughan 2005; Roll-Hansen 2000).
In contrast to Schroedinger, Bohr (and subsequently Delbrueck) did not seek to reduce biology to physics; instead, the goal was to understand how each discipline complemented the other (Delbrueck 1949; Sloan and Fogel 2011).
And the import of experimental methods from physics to biology raised the question of the relation between those disciplines.
Molecular biology’s classical period began in 1953, with James Watson and Francis Crick’s discovery of the double helical structure of DNA (Watson and Crick 1953a,b).
As suggested in the brief history above, experimentation figured prominently in the rise of molecular biology (see the entry on experiment in biology).
X-ray crystallography allowed molecular biologists to investigate the structure of macromolecules (see Celebrating Crystallography in Other Internet Resources).
For Schroedinger, biology was to be reduced to the more fundamental principles of physics, while Delbrueck instead resisted such a reduction and sought what made biology unique.
Muller’s shift from Mendelian genetics to the study of gene structure raises the question of the relation between the gene concepts found in those separate fields of genetics.