Two schools:
Structuralists
3-D, biochemistry, analog
Informationists School,
1-D, genetics, digital
W. H. Bragg and W. L. Bragg (father and son)
invention of x-ray crystallography (1912)
W. T. Astbury, J. D. Bernal (Bragg's pupil)
structural analysis of proteins and nucleic acids
Linus Pauling
alpha-helix (1951)
novel approach - guesswork plus model building
Max Perutz, John C. Kendrew
structures of hemoglobin and myoglobin
Nonrevolutionary influence on general biology
preoccupation with structure rather than information
down-to-earth view of the relation of physics to biology - all biological phenomena can be accounted for in terms of conventional physical laws
There was hardly any common ground between genetics on the one hand, and physics and chemistry on the other.
Niels Bohr
Some biological phenomena might turn out to be not accountable wholly in terms of conventional physical concepts
'Uncertainty principle' - the impossibility of describing the quantum of action
The encounter of what appears to be a deep paradox eventually leads to a higher level of understanding.
The difficulty to understand life in physical terms is 'that the conditions holding for biological and physical researches are not directly comparable, since the necessity of keeping the object of investigation alive imposes a restriction on the former, which finds no counterparts in the latter. Thus we should doubtless kill an animal if we tried to carry the investigation of its organs so far that we could describe the role play by single atoms in vital functions'
Max Delbröck (Bohr's pupil)
Genetics is a domain inquiry in which physical and chemical explanations might be insufficient.
Romantic expectation for the discovery of new physical principle(s) ('other laws') from the study of genetics.
In search of complementarity and paradoxes.
Gene as a molecule -
size estimated from genetic studies (physical mutagenesis) comparable to those of the largest known molecules
stability, low mutation frequencies,
mutations - discontinuous, saltatory changes
1938 - chose bacteriophage as ideal objects for study of biological self-replication, and the physical basis of heredity.
Erwin Schrödinger
'What is Life' (1945)
A new frontier was now ready for some exciting development. 'The inability of the present-day physics and chemistry to acount [for the events which take place in a living organis] is no reason at all for doubting that they can be accounted for by those sciences.'
The real problem requiring explanation is the physical basis of genetic information.
The dimensions of genes are not very large relative to those of atoms.
Chromosomes as a periodic crystal composed of a succession of a small number of isomeric elements, the exact nature of succession representing the hereditary code.
The phage group
Max Delbröck, Salvador Luria, Alfred Hershey, Martha Chase
Introduction of bacterial and bacteriophage genetics
'though the immediate conclusions drawn from the results of the experiments of the romantic phase were almost always right, the more general and really interesting speculations built upon these first-order conclusions were mostly wrong.'
No paradoxes cropped up.
James Watson and Francis Crick
Discovery of double helix
Structuralism and Informationalsm joined hands
'introduced genetic reasoning into structural determination, by demanding that the evidently highly regular structure of DNA be able to accommodate the informational element of arbitrary nucleotide base sequence along the two paired polynucleiotide strands.'
'opened up enormous vistas to imagination'
formulated the central dogma
DNA -> RNA -> protein
genetic code for translation of nucleotide sequences to amino acid sequences
oligonucleotide 'adaptor' molecule -> transfer RNA
François Jacob and Jacques Monod
messenger RNA (with Crick et al.)
operon
Romantic phase
'still groping for the still unimaginable'
The two Schools had less to say to each other in terms of real intellectual communication than one might expect
Still romancing with possible paradox which may help revealing 'other laws of physics'
Dogma phase
'test and elaboration of the clearly stated central dogma'
The two Schools began to converge.
'No paradoxes had come into focus, no "other laws of physics" had turned up'. Eventually all hopes for paradoxes were abandomed.
'to iron out the details'
A formidable (but 'can at least be imagined') detail
differentiation
The higher nervous system
'the most ancient and best knwon paradox in the history of human thoughts: the relation of mind to matter, or free will to determinism
Perhaps, history may be repeated in the approaches to the studies of brain:
Structuralism vs. Informationalism
Is memory an analog structure or digital code?
Created on ... octobre 04, 2003