Genetic Analysis 2816 FROM GENOTYPES TO PHENOTYPES TO STEREOTYPESTell me your genes
and I’ll tell you
who you are
(from a TV program)A major achievement of Mendel’s experimental design was his ability to supersede
specific traits and draw analytic, general conclusions on the mechanisms of hered-
ity, irrespective of how the alternative properties unfold. Mendel’s method allowed
him to ignore the relationship betweenFaktornand traits. Contrarily, de Vries’s
Intracellular Pangenesistheory was a theory of development and evolution of or-
ganisms as assemblies of distinct characteristics. MendelianFaktorenbecame part
of his notion of “unit characters” in hisMutationstheorie(see section 2). Thus,
research of gene expression from its very beginnings rose beyond theorganismas
the referent and concentrated on the development and function ofunit-characters,
differing from research in embryology that traditionally was an organismic, top-
down discipline. However,Entwicklungsmechanikwas introduced to promote a
reductionist notion of development, as heralded in Roux’s introductory manifesto
to his newArchiv:
In accordance with Spinoza’s and Kant’s definition of mechanism, every
phenomenon underlying causality is designated as amechanical phe-
nomenon;... Since only phenomena underlying causality are capable
of investigation,... and since the production of form constitutes the
essential feature of development,... we must trace back each individ-
ual formative process to the special combination of energies by which
it is conditioned, or, in other words, to itsmodi operandi;... Those
modi operandi, to which we reduce organic formative processes, and
hence also the energies which condition them, may be identical with
those which underlie inorganic or physico-chemical processes. [Roux,
1904/1986, 108–111]Still, Roux was very much aware of the complexity of living organisms, and
warned that, “Among biologists there is a tendency derived from inorganic sci-
ences,to regard the hypothetical deductions which appear to us to be the “simplest”
as having the greatest probability for the very reason that they seem so simple”
[Roux, 1904/1986, 119]. Thus developmental mechanists were patently in a con-
stant conflict:Conceptuallythey must accept that living organisms are complex
entities that cannot be reduced to simple physico-chemical principles, yetmethod-
ologicallythey must apply physico-chemical experimental procedures to uncover
causes, ormodi operandi:
“Incidit in Scyllam, qui vult vitare Charybdim” is particularly appli-
cable to the investigator in the field of developmental mechanics. The