Information Technology Reference
In-Depth Information
Aaron Klug, Rosalind Franklin, Kenneth Holmes and others contributed greatly to the
establishment of molecular biology. I do not need to list their enormous achievements.
If we take a large molecule, for example the protein lysozyme, it contains C, H, O,
N, S atoms in definite numbers and so should appear as a region in the phase diagram of
this 5-component system. It would probably be in a meta-stable energy minimum.
However, this is clearly unrealistic and lysozyme is much better considered as being
specified by a number which represents its amino-acid sequence, which is effectively its
address in phase space. Given the sequence, lysozyme can be now be made by adding the
right amino residues in the right order. That is, it has a description. Information is stored in
such meta-stable systems.
The proteins of life are a very special and minutely small subset of all possible
amino-acid sequences characterised by being able to fold up into a unique configuration.
7. The double helix
Darwin and Mendel recognised the discrete nature of the hereditary substance but could get
no further without access to the levels below those provided by optical microscopy.
The 50th anniversary
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of the spatial structure of the DNA double helix has ensured
that the circumstances of the discovery should now be well-known. I remember opening the
copy of Nature for 25 April 1953 and reading the three papers disclosing the double helix,
Crick and Watson's paper ending with the sentence:
"It has not escaped our notice that the
specific pairing we have postulated immediately suggests a possible copying mechanism for
the genetic material"
and thinking, yes, of course, it must be something like that. An
immediate entry to the mechanism of heredity had opened, just as van't Hoff's vision in
1874 of the tetrahedral carbon atom had opened up organic chemistry, making it clear that
is was the arrangement of atoms in three-dimensional space that was the determining factor
for molecules (although Pasteur had demonstrated optical enantiomorphism in 1848,
picking left- and right-handed crystals, and this implied spatial structure).
8. Dialectics
The key theme of this workshop is the relationship between information and structure. The
more we look into it, the more complicated it gets. A very informative modern survey of
the interaction between
“nature and nurture”
has been provided by Matt Ridley
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. The
conflict has been fought at all levels from the molecular to the politics of agriculture and
education. The Lysenko affair in the Soviet Union was one acute manifestation, but there
are still deepening conflicts with religious views.
The basic idea, that one structure should be a description of another, but both
composed of atoms subject to the same laws of chemistry, has been revolutionary
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Real Space Representational Space
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Genotype
Phenotype
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Projection
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Comparison Manipulation
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Restoration
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