Biology Reference
In-Depth Information
4
The Contradiction in Genetic
Determinism
S
UMMARY
. In contrast to theoretical predictions of genetic
determinism, experimental data obtained over the last forty
years show that interactions between biological molecules are
not specific and are immensely varied, with one molecule being
able to interact with a large number of partner molecules.
There are several causes for this phenomenon. The same amino
acid sequences corresponding to the binding sites between mol-
ecules are present in a great many different proteins, which pro-
duces a very large number of possible combinations of potential
interactions, increased even further by less powerful interac-
tions involving sequences said to be 'degenerate'. However,
there is a more radical cause of non-specific interactions. It is
now known that many proteins do not have an ordered three-
dimensional structure necessary for producing specific interac-
tions. They can adopt a multiplicity of conformations permitting
a huge number of interactions, which generate different macro-
molecular structures or cascades of interactions. This directly
challenges the principle of order from order of genetic deter-
minism, according to which biological organisation is sup-
posed to arise from an underlying molecular order. All the
molecular cascades are interconnected one with another, and
simply mapping the networks they constitute cannot explain
the way a cell functions. Molecular networks must themselves
be subject to some kind of regulation which remains to be elu-
cidated. To solve this problem, biologists have inferred that the
overall structure of the cell restricts the combination of mole-
cules, but such an explanation is holistic. It comes down to
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