We have learned that the very basis of
biological order, of specificity and diversity, is a sequence of a few
small molecules. We have learned that nucleic acid, considered on
the time scale of the organism, is the stable, permanent structure
responsible for the specificity and for the reproduction of specificity.
But, considered on the time scale of the world, nucleic acid is the
varying structure responsible for mutations and evolution.

Stability and variability reside in the same structure. This dual
function of the genetic material is one of the important aspects of
life.

Nucleic acid is the blueprint for the synthesis of specific proteins,
which in turn are the catalysts for the synthesis of essential
metabolites. Nucleic acids and enzymes are, from a functional point
of view, complementary macromolecules in the sense that one
cannot be produced without the other.

The organism, or the cell, is a complex molecular society in which
macromolecules and groups of macromolecules are interacting. The
functioning of each enzyme or group of enzymes, so as their syn-
thesis, is controlled by the product of their activity, or better by the
needs of the organism. Each group possesses its own regulatory
system. All the groups and all the various regulating systems in-
teract.

As a result of evolution, an elaborate system of a feedback mech-
anism has developed. The functioning of the organism reflects the

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