Philosophy of Biology

Genetic Analysis 295

9 CONCLUSION

In an editorial in 1995, “Homage to the chromosome”, Joseph Gall wrote:

Biological organisms, unlike complex inanimate systems, contain infor-

mation that regulates their day-to-day activities, and, more remark-

ably, lets them produce new organisms from single cells. That this

information resides in the chromosomes was established 75 years ago

... missing from the classical account, however, was any understand-
ing of the nature of the information carried by the chromosomes. That
gap was, of course, filled by later spectacular advances in molecular
genetics, which showed that a gene is a segment of DNA whose linear
sequence of nucleotides specifies the linear sequence of amino acids in
the protein.... But just as a book is more than a random assortment
of words, chromosomes are more than simple repositories of gene se-
quences. They must contain regulatory information for turning genes
on and off and they must control their own replication, repair, packag-
ing, as well as the complex movements they carry out during mitosis
and meiosis. [Gall, 1995]

Gall here expressed in a nutshell the achievements of genetic analysis together
with its methodological successes and epistemological blind alleys.
Genetic analysis in the first decades of the twentieth century had to struggle for
its independence [Falk, 1995b]. It achieved this to a large extent by concentrating
its efforts on the phenomenological aspects of the mechanical causes of inheritance,
by applying a strict reductionist methodology. By and large, genes (and their
organization) were treated as intervening variables, or as hypothetical constructs,
“because at the level at which the genetic experiment lie, it does not make the
slightest difference whether the gene is a hypothetical unit, or whether the gene
is a material particle” [Morgan, 1935]. But the wider context was not neglected,
whether in the search for their physico-chemical structure and function, or in their
role in the evolution of populations and species.
At the time when genetics achieved its secure independence, Morgan asserted:

The story of genetics has become so interwoven with that of experi-

mental embryology that the two can now to some extent be told as a

single story.... today their interdependence is so obvious that the

geneticists takes for granted the main outlines of the facts of embryol-

ogy, and the embryologist is coming to realize his dependence on the

evidence from genetics. [Morgan, 1934, 9]

The course opened by Beadle and Tatum’s “one gene — one enzyme” and their
analysis of metabolic pathways inNeurosporadirected wide attention to the study
of gene-function in the tradition of genetic analysis of discrete genes, rather than
that of dealing with developmental systems. The presentation of the molecular