Moss - What genes cant do - 2003 (522929), страница 15
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Nor certainly would it be other than shameless sleight of hand to assert thatgenes thereby simultaneously possess both kinds of information. Yet, inorder for the claim to be redeemed that genes possess the informationfor making an organism, something very much like this would have tobe the case. The realization of genetics understood not as a practice ofinstrumental reductionism but rather in the constitutive reductionistvein, would require the ability to account for the production of the phenotype on the basis of the genes. This is clearly what the rhetoric of the“genetic program,” “genetic blueprint,” and so forth implies. Has thediscovery of the structure and mechanisms of DNA provided what classical genetics alone could not do—an explanation for the developmentof the phenotype? Chapter 3, following some historical considerationson the acquisition of the information metaphor in chapter 2, will furtherscrutinize the empirical adequacy of the idea that genes contain the information for making a phenotype.2The Rhetoric of Life and the Life of RhetoricIn calling the structure of the chromosome fibers a code-script we mean that theall-penetrating mind, once conceived by Laplace, to which every causal connection lay immediately open, could tell from their structure whether the egg woulddevelop, under suitable conditions, into a black cock or into a speckled hen, intoa fly or a maize plant, a rhododendron, a beetle, a mouse or a woman .
. . Butthe term code-script is, of course, too narrow. The chromosome structures areat the same time instrumental in bringing about the development they foreshadow. They are law-code and executive power—or, to use another simile, theyare architect’s plan and builder’s craft—in one.—Erwin Schrödinger, 1944Gene-P or Gene-DI have argued in the first chapter for a bipartite understanding of themeaning of “genes.” Genes may be accorded the preformationistic statusof being prior determinants of some phenotype (Gene-P) but only for alimited number of traits and only in the spirit of instrumental utilitywhen some local benefit is to be had in doing so. The use of geneticprobes for certain mutations, such as those associated with cystic fibrosis (CF), might exemplify this usage.
Identification of cystic fibrosis (CF)genes, those alternative forms of the DNA template for a certain transmembrane, chloride channel protein that are implicated in the onset ofCF, tells us little about the developmental physiology (including epithelial cell–microbial interactions) that actually results in CF disease, but ithas proven to have some instrumental value in predicting an undesirablehuman condition. Even in the case of CF the value of the instrumentalpreformationist approach tails off when one is considering the wide52Chapter 2spectrum of different CF mutations (now up to 9941), the combinatorial complexity associated with correlating phenotype with the particularpairs of CF variants that could occur, and the observed failure of thesame pairs to result in the same phenotypes in different individuals.The second meaning of genes (Gene-D) refers to a segment of DNAcharacterized as a transcriptional unit that provides template information for some range of polypeptides but whose relationship to a phenotype is always in itself indeterminate.
In this view, genes, in order to berelated to an ultimate phenotype, must be situated in the dynamic developmental context and environmental milieu of an organism. As one category of internal resource, one type of molecule (or part thereof) amongmany, genes are not accorded any form of necessary causal privileging.I refer to this perspective, which draws on both the latest knowledge ofbiochemical-molecular interactions as well as that of the dynamics ofcomplex systems, as “the new epigenetics.”The Conflation of Gene-P and Gene-D with Rhetorical GlueMy analysis of the double meaning of genes is meant to serve as a counterpoint to what I take as an attempt to have it both ways, that is, tounderstand genes as similtaneously both discrete segments of DNA andcausally privileged determinants of phenotypic outcomes. The engagement of textual metaphors with which to characterize genes as differentfrom other biological material, i.e., as text—program, blueprint, codescript, books of life, and so forth—has been integral to this conflationary construction.
As text, and perhaps only as such, genes can beconceived as molecules and yet evade the circumstantial contingencies,the “fateful winds,” which most pieces of matter find hard to resist. Itis as matter-text that genes and DNA ascend to the status of sentiencyand agency, as matter with its own instructions for use, and furthermore,as the user too. If such a view really exists (and indeed flourishes withincreasing significance for social policy, biomedical research and development, and human self-understanding) as I suggest, then it must haveemerged from somewhere and presumably (hopefully?) stand in somerelationship to empirically accountable claims about the way things are.The purpose of this chapter will be to uncover at least some of the moreThe Rhetoric of Life and the Life of Rhetoric53important root sources of this idiom, to try to clarify what sort of semantic strings are attached to it, and to make salient those claims to whichit could and should be held accountable.There is an additional subtext that can be made more explicit.
Theidea, advanced by post-modern critics of science such as Donna Harraway and Richard Doyle, that technologies of language construction—the so-called rhetoric of science—can be as instrumental in the shapingand promulgation of a certain research program as, say, gel electrophoresis or any other central piece of instrumentation, is a view withwhich I have much sympathy. But while these critics often take upthe tone of the indignant, if surreptitiously bemused, muckraker revealing a scandal, they abstain, as if required by some categorical imperative, from defending any truth claims at the level of the subject matterof their text.The scandal of scandals, it would seem for these critics, is thatthe rhetoric of science moves inexorably, always charting its own course.Yet in seeking to clarify the claims and arguments upon which a certainrhetoric, such as that of the genetic text, could be rationally defendedor undermined, I am seeking to penetrate the Teflon autonomy ofthe rhetorical “trope” (even if with the aid of other rhetorical tropes).My discussion in this chapter is then both a critique of the rhetoricassociated with scientific research programs and a contribution to aconversation about how to criticize the rhetoric associated with scientific research.The Self-Executing Code-ScriptErwin Schrödinger’s 1944 monograph, What is Life?, was described byGunther Stent (1995) as having played a mobilizing role, an Uncle Tom’sCabin (if you will), in rallying a new generation of physicists andchemists to the cause of working out the nature of genetic substance.
Itis well known that What is Life? was influential for both the young JamesWatson and the young Francis Crick (Portugal & Cohen 1977, Judson1979). And it was one of the very few points of background commonalty between them. I suggested at the end of chapter 1 that the only alternative to recognizing the need for recontextualizing molecular genes54Chapter 2(Gene-D) in a renewed theory of epigenesis would have to be some theorywhich depicts the genotype as containing its own instructions for use.Only if the entire process of ontogeny can be understood as progammatically prespecified in the genotype can epigenesis be relegated to akind of epiphenomenon of the genotype, an idea which is unfortunatelyoften promoted by naive readings of Waddington’s term “epigenetics.”The epigraph above reveals that Schrödinger provided just such a visionand just such a metaphor with his notion of a code-script that is at onceself-executing: “architect’s plan and builder’s craft—in one.”Schrödinger, the Nobel prize–winning (1933) cofounder of modernquantum theory, had his attention drawn to biology during a 1935lecture by Max Delbrück in Berlin (Judson 1979).
Delbrück was theproduct of an elite academic family in Berlin and most highly influencedin his style and thinking by Niels Bohr. He attributed his first stimulusfor thinking about biological issues to a discussion with Bohr in 1931concerning the bearing of quantum mechanics on biology (Olby 1974).Delbrück came to the United States in 1937 as a physicist. By 1940he had established a research program with Luria and Hershey into theinvestigation of the genetics of bacterial viruses. The team becamefamously known as the “Phage Group” (Portugal & Cohen 1977, Judson1979).
Delbrück, one of the most influential of the physical scientists tomake the move to molecular biology, was also the most prominent ofthose early molecular biologists whom John Kendrew (1967) classifiedas “informational” as opposed to “structural.” The structuralists weremostly English (as was Kendrew) and generally x-ray crystallographers(as was Kendrew).
The notable exception was Linus Pauling, anAmerican at Caltech, who approached the structural analysis of biological macromolecules as a problem in quantum theory. Delbrück,guided by his goal of elucidating the physical basis of hereditaryinformation transfer, chose to study the bacteriophage.The “phage,” as it became affectionately known, recommended itselfas apparently the simplest entity that participated in some form ofheritable information transfer. It consists of only two types of biologicalmacromolecules, protein and nucleic acid (DNA). Evidence was providedby Avery and coworkers in the mid-1940s that DNA was responsible foraffecting the bacteriophage-induced “transformation” of bacterial cells,The Rhetoric of Life and the Life of Rhetoric55yet, largely because DNA appeared to be information-poor, the Averyresults were relegated to the back-burner.
Proteins consist of 20 different monomeric subunits (amino acids) as compared to the merely fourunits of DNA, and thereby proteins appeared to Delbrück to be the morelikely basis of hereditary information. For Delbrück, the leader ofthe informationist camp of the physicists-cum-molecular biologists, theheuristics of “information” pointed away from DNA and the “path tothe double helix.”Delbrück’s influence on Schrödinger can be interpreted in differentways and has been the subject of some differences of opinion. RobertOlby (1974), mostly taking issue with Gunther Stent’s characterizationof the so-called romantic phase of molecular biology, has argued thatSchrödinger was not seeking the discovery of new fundamental laws ofphysics in biology and/or the realization of Bohr’s principle of complementarity in the life sciences, but rather he was attempting to show thatthe quantum theory of the chemical bond could account for the requisite stability of biological order in a way which classical statistical physicscould not:He [Schrödinger] could demonstrate that even if genes were not chemical molecules the physicist could still allow them to have stability and mutability, becauseof quantum mechanics.
Now a physicist reading this book could get excitedabout genetics. Schrödinger made the facts of genetics meaningful to the physicist. He did not offer his readers the bait of a fresh mutually exclusive complementarity relationship, as did Bohr. He offered them “other laws” to be sure,but not of the kind Bohr envisaged. They would be related to known physicallaws, just as the laws of electrodynamics were related to the more general lawsof physics (Olby 1974).An examination of Schrödinger’s text reveals that Olby is correct in hisappraisal of Schrödinger’s motivation for writing the book. Olby (1974),however, does not adequately analyze Schrödinger’s warrant for movingfrom his quantum mechanical arguments to his promotion of the idea ofa hereditary code-script, yet he celebrates Schrödinger’s “concept of anhereditary code-script” as that which “we can see in retrospect as themost positive and influential aspect of this little book.” Influential?Without a doubt.
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