They make humans unique yet ordinary, sell Levis and excuse promiscuity. Sarah Franklin looks at the confusing messages of gene mania.

The fact that the rough draft of the human genome shows we have many fewer genes than anticipated underscores once again our tendency to overestimate their determining role in human biology or society. The 32,000 human genes - only some of which have been absolutely confirmed - are altering many of the basic assumptions that have shaped our understanding of genetic function.

Most notably, it is evident that numbers of genes alone do not determine complexity of behaviour or phenotype: humans have only about twice as many genes as fruit flies and 60 per cent of human genetic sequences resemble those of worms. Statistics showing that humans have 98 per cent of their DNA in common with chimpanzees and 35 per cent in common with daffodils might be considered powerful evidence that it is clearly not genes that account for human uniqueness, never mind subtle variations in personality or huge differences in build, such as height. Yet, at the same time that we are being told that genetics is complex, popular culture, as well as science and medicine, reflects a powerful belief in genetic determinism - in the genes as a key, or blueprint, or underlying structural code explaining everything from intelligence to shyness. As our society becomes post-genomic, the gene continues to be reinvented as a universal human code, a magical sign, a kind of 21st-century fetish.

There are several reasons for our desire to anchor explanations in conveniently singular locations known as "genes". It is, for example, obvious that prenatal screening for harmful genes can offer greater control over reproductive health. People can choose to avoid a pregnancy affected by a disease caused by a single gene, such as Duchenne muscular dystrophy, although such diseases are very rare and having the gene for a specific condition does not necessarily mean it will be expressed. Moreover, in cases such as Huntington's disease, where there is a 100 per cent correlation between the gene and the disease, neither the severity of the condition nor the time of onset can be reliably predicted by genetic diagnosis alone.

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Actual encounters with genetic information are rarely as simple as the theory might suggest. Much genetic information is ambiguous: even the presence of an entire extra chromosome may have no effect, while minor, almost undetectable, changes such as translocations can be severely debilitating. This makes risk prediction a very precise but often inaccurate art. A decision that has to be made on the basis of ambiguous information risks producing a sense of confusion, or anguish, rather than a sense of increased control.

There is no doubt that the human genome project will be of tremendous value in the effort to increase medical and scientific understandings of gene structure and function, and the broad patterns of both human similarity and difference. However, gene expression continues to become more elusive even as it is brought into closer focus, leading to an inevitable pressure to understand genes less in and of themselves than as protein events in much longer sequential chains. This view of the gene as one protein event among others, known as proteomics, or the study of protein interaction, has become an important new context of medical and biological research.

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For example, the pioneering research of the team that cloned Dolly the sheep utilised a technique that directly contradicted the model of the gene as the designer molecule authoring subsequent chains of cellular development. In contrast to the idea that proteins do what genes tell them to, the team demon-strated that "DNA does what it is told to do" by the egg cell cytoplasm, which can reprogram DNA to undertake a much wider range of functions than was imagined possible. A similar principle guides the expanding field of tissue engineering, in which reconstructed cells and cell lines are used as the "smart" petri dishes in which to culture bespoke cellular products for use in the treatment of disease and possibly organ replacement. Science publications have celebrated the ability of specialised cells such as bone marrow, to de-differentiate and re-direct their growth into heart muscle or pancreatic tissue. In these experiments, genes are more the messengers than the little Wizards of Oz orchestrating vast genomic architectures.

The ability to re-harness cellular functionality and to scientifically engineer complex protein pathways in which genes play a more minor "programming" role, exists somewhat in tension with the ongoing "gene-omania" accompanying the human genome project. This bi-polar attitude to genes parallels a sociological context in which genes have simultaneously become a new language of determinism and a more amorphous set of less reductive representations.

For example, evolutionary psychology's claims about the genetic legacy of our evolutionary heritage are used in a problematic manner to legitimise anti-social behaviour such as male promiscuity and sexual aggression. While such claims may bear little relation to the findings of actual gene mappers active in the human genome project, they nonetheless reinforce a sense of genes as the essence or determining code of human behaviour and, when it comes to studies `that claim to identify genetic differences in intelligence, inevitably raise concerns about racial discrimination and eugenic selection. At the same time, a growing social fascination with DNA is evident in advertising campaigns, such as the Levis "re-engineered" jeans series, which celebrates mutation as a form of brand uniqueness. In popular culture, as in genetic science, there are many genetic idioms, that do not resolve any more easily into a single picture of genetic determinism than do the myriad highly technical versions of what kind of molecular function defines a gene.

One of the main reasons genes are appealing as explanation-systems-unto-themselves is simply the extent to which the idea of the gene condenses already commonsensical beliefs about human uniqueness and individuality. The human genome project does not need to tell us we are a complex species simply by demonstrating we have significantly more genes than do apes or pigeons. It is not the quantity of genes that matters, but their quality. Genes' attraction as explanatory vehicles, immune to contradiction, is their uniqueness, and the genes-are-unique rationale is completely tautological, in the way all highly effective essentialisms always are. Genes make us unique, and our uniqueness is in our genes. The nearly seamless public acceptance of forensic DNA technology, or at least its underlying logic of identification of individuals through their DNA, attests to the breadth of the assumption that each individual is unique, and has unique DNA (except identical twins). Similarly, the human species is unique, and has unique DNA (except for what we share with mice and worms).

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In addition, the concept of genetic inheritance recapitulates the biological model of sexual reproduction according to which a child is a (unique) combination of shared substance from two parents. The concepts of genetic identity, genetic differences, genetic blueprints or genetic profiles are both fascinating and worrisome precisely because they re-deploy very familiar assumptions about what a person is, and how we came into being.

The difference genomics introduces is the level of scientific abstraction. The idea of the blood tie, steeped in a history thick with European ideas about trees, soil and lineage, is more densely metaphorical than the much more recent concept of the gene, with its highly technical scientific pedigree and aura of professional expertise. It is this discrepancy, between everything intimate and familiar genes signify, and everything unfamiliar about the language in which they do so, that is in the midst of being negotiated at a range of levels in contemporary society - from debates about genetically modified food and the environment to questions about human genetic medicine and reproductive choice.

It is not because scientists have declared that our genes are the essence of our human-ity, or that the human genome project is man's second genesis, that genes are powerful cultural signifiers of human essence. It is equally unlikely that our becoming post-genomic - our genes revealed to be more what we have in common with primitive non-vertebrates than what makes us distinctive - will make genes any less magical in their ability to signify human uniqueness or individuality. Both within genetic science and within wider society, genes are acquiring a wide range of new meanings, the profusion of which both reproduces and transforms the cultural traditions that made genes appear so intriguing and elusive as scientific and technical objects to begin with.

Sarah Franklin is reader in cultural anthropology at Lancaster University and writes on technology and culture. She is undertaking an ethnographic study of pre-implantation genetic diagnosis funded through the Economic and Social Research Council Innovative Health Technologies programme.

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