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In the Beginning Was the Word

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Science  16 Feb 2001:
Vol. 291, Issue 5507, pp. 1263-1264
DOI: 10.1126/science.1057124

Who Wrote the Book of Life? A History of the Genetic Code Lily E. Kay Stanford University Press, Stanford, CA 2000. 470 pp. $60, £45. ISBN 0-8047-3384-8. Paper, $24.95, £17.95. ISBN 0-8047-3417-8.

It seems impossible to do science without metaphors. Biology since the 17th century has been a working out of Descarte's original metaphor of the organism as machine. But the use of metaphor carries with it the consequence that we construct our view of the world, and formulate our methods for its analysis, as if the metaphor were the thing itself. The organism has long since ceased to be viewed like a machine and is said to be a machine. The ways in which the metaphors of biology have molded the concepts and experiments of the science have been a preoccupation of the historian of molecular biology Lily Kay. In Who Wrote the Book of Life? her most recent and unfortunately final book (she died of cancer in December), Kay asks how the view that DNA is “information” that is “written” in a “language” whose “words” are in “code” has driven the research program and claims of molecular biology.

Kay's analysis of the history of molecular genetics is poststructuralist. That is, while not denying the objective reality of genes, proteins, and cellular elements, it is “grounded in the conviction that once a commitment to a particular representation of life is made—material, discursive and social—it assumes a kind of agency that both enables and constrains the thoughts and actions of biologists.” Unfortunately, the outline of this claim in the early part of the book makes a formulaic use of the special jargon of poststructuralist theory, a jargon that will be impenetrable to any biologist not possessed of a considerable education in literary theory. But the biologist should persist, because the central chapters on “Genetic Codes in the 1950s” and “Writing Genetic Codes in the 1960s” present a compelling case for the ways in which the purely theoretical analysis of DNA as a code led to the determinative experiments that demonstrated the mechanism by which amino acid sequences are specified and constructed.

Many biologists in the late 1950s (I among them) regarded with a certain contemptuous hauteur the attempts of renegade physicists to illumine the relation between gene and protein by engaging in the sort of cryptanalysis that became so romantic as a result of the wartime triumphs of Bletchley Park. But Kay shows quite convincingly that, although these codebreaking techniques could not in themselves provide the right answer, the view of DNA as code and amino acid sequence as plaintext was absolutely essential in the very conception of the critical experiments at the beginning of the 1960s. The brilliant paper by Crick, Barnett, Brenner, and Watts-Tobin, which demonstrated so elegantly that the DNA sequence was processed from a fixed starting point using each successive non-overlapping triplet to determine the next amino acid in the chain, and Nirenberg and Matthaei's path-breaking demonstration that poly-U RNA in an in vitro synthetic system resulted in the construction of a polypeptide consisting solely of phenylalanine, would have been conceptually impossible without the metaphor of the code. This, then, raises the problem of the counter-factual conditional that plagues all attempts to understand history: What if? What would have happened had the language metaphor never taken hold in molecular genetics? Would we now be ignorant of the details of the relation between DNA and protein? Would we have a different understanding? Would we know more about the world? or less?

Some contradictions surface in Kay's attitude toward the metaphors. At first, “code” always appears in inverted commas, but as the argument proceeds Kay herself uses the concept of code unproblematically. While claiming that we cannot really dispense with metaphors, she herself tries to do so by repeatedly saying that the DNA triplet-amino acid relation is merely a correlation. But that is surely wrong. DNA and amino acid sequences are not simply correlated, they are connected by a causal mechanism. And in the causal pathway, DNA sequence appears before the amino acid sequence.

A good deal of discussion in the book is devoted to showing why the metaphors of “code,” “language,” and “information” can be so misleading if taken as isomorphic with the phenomena of molecular genetics. This is especially a problem if these nonbiological notions are taken in their modern analytic and scientific contexts. If “information” is the information of Shannon-Weaver information measures; if “language” is what Jakobson, Chomsky, and other linguists take it to be; if “code” is what the Enigma machine was meant to create; then as Kay so clearly shows, we are badly misled by applying these measures to DNA. But, as she says, “code,” “language,” and “information” are themselves metaphors, terms appropriated by science and technology and given special content for special purposes. For an old-fashioned epistemologist, to say that DNA contains determinative information about amino acid sequences is simply to say that a knowledge of the DNA sequence is sufficient to provide knowledge of the amino acid sequence but not vice versa. The best way to protect ourselves against the damage of metaphors is to allow the models on which they are based to have as little specific content as possible while still allowing them to serve a constructive purpose. As Arturo Rosenblueth and Norbert Wiener once noted, “The price of metaphor is eternal vigilance.”

The real damage done by the idea of DNA as “The Book of Life” is laid out in the last chapters of Kay's book. It is the elevation of DNA to the status of a master molecule, one which determines in some autonomous way the very nature of living organisms. The erroneous description of DNA as “self-replicating,” as “making” proteins, and as “determining” organisms is repeated over and over in service of the hegemony of the gene. But DNA is not self-replicating any more than a letter put into a photocopier is self-replicating. DNA sequence does not specify protein, but only the amino acid sequence. The protein is one of a number of minimum free-energy foldings of the same amino acid chain, and the cellular milieu together with the translation process influences which of these foldings occurs. (Even Kay sometimes writes “protein” when she means “amino acid sequence.”) And organisms are not determined by their DNA but by an interaction of genes and the environment, modified by random cellular events. Kay ascribes most of the fetishism of DNA as the ultimate information on which life is built to the tremendous prestige that technology acquired during World War II, to the immense amounts of money poured into biological research by technology-oriented government agencies, and to the impetus given to technology by the appearance of Sputnik. I would add that the notion of the primary role of the DNA “blueprint” and the merely mechanical, secondary role of the cell machinery that uses that blueprint for production is another form of the deep cultural prejudice (characteristic of modern capitalism) that mental labor is superior to mere physical labor, a prejudice that is replicated in the entire structure of laboratory life.

Biologists skeptical of the poststructuralist theories of a mere historian like Lily Kay might do well to consider the opinion of François Jacob on the matter:

But science is enclosed in its explanatory system, and cannot escape from it. Today the world is message, codes and information. Tomorrow what analysis will break down our objects to reconstitute them in a new space? What new “Russian doll” will emerge? [The Logic of Life, (Pantheon, New York, 1973).]

But then again, what can you expect from a Frenchman?

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