278 Raphael Falk
stract gene. In contrast, the fundamental unit of molecular genetics
is a concrete chemical molecule, the nucleotide, with the gene being
relegated to a role of a secondary unit aggregate comprising hundreds
or thousands of such nucleotides. [Stent, 1970, 910]... since it was already taken for granted that the genetic information
is held in the form of a particulate nucleotide base sequence in DNA, it
now became clear that themeaningof the particulate nucleotide base
sequence making up a sector of DNA corresponding to a gene could be
nothing other than the specification of an amino acid sequence of the
corresponding protein molecule. [Stent, 1970, 925]
Attempts to formally reduce the classical gene to the molecular gene [Rosenberg,
1985] (see also Sarkar [1998]; Schaffner [1976]) apparently only supported the claim
of discontinuity between the classical gene and the molecular gene. Although
another two decades were needed, genetic engineering seemed to have achieved
this fit of defining a gene as a sequence of DNA, “which in itself is indeterminate
with respect to phenotype” [Moss, 2003, 46]. Ironically, this notion from the
DNA-sequence to the trait was called “reverse genetics” though this should have
been called “forward genetics”, whereas the classical approach of inferring from
the phenotype to the genotype is the genuine “reverse genetics”.
This dichotomy of the gene as that unit which is identified by a phenotypic
“marker” versus the gene as a defined DNA sequence has been developed to its
extreme by Lenny Moss:
The rhetoric of the gene as code and information,... turns on...
a conflation of two distinctly different meanings of the gene. When
scientists and clinicians speak of genes for breast cancer, genes for
cystic fibrosis, or genes for blue eyes, they are referring to a sense of
a gene defined by its relationship to a phenotype... and not to a
molecular sequence.
It continues to be useful, in some contexts, to employ this usage of
the word “gene.” To speak of a gene for a phenotype is to speak as
if, butonlyas if, it directly determines the phenotype. It is a form of
prefomationism but one deployed for the sake of instrumental utility.
I call this sense of the gene — Gene P, with the P for preformationist.
...
Quite unlike Gene-P,Gene-D is defined by its molecular sequence. A
Gene-D is a developmental resource... which in itself isindeterminate
with respect to phenotype. To be a Gene-D is to be a transcriptional
unit on a chromosome within which are contained molecular template
resources. [Moss, 2003, 44-46]This duality of concepts may have been justified as long as the “classical molec-
ular gene”, a unique sequence of DNA that is transcribed and translated into a