ABSTRACT

The conceptual history of the gene, beginning as an inference from the observation of Mendelian regularities in inheritance at the turn of the last century and reaching an apex with the unraveling of its biochemical structure by Watson and Crick in 1953, figured for a long time as a standard example of successful reduction in the life sciences. This has variously led to highly reductionistic interpretations of Darwinian evolution. But ever since its internal makeup was known, the gene has also become an increasingly problematic entity. Indeed, a conceptual crisis has arisen during the last twenty years as a result of the discovery of overlapping genes, alternative splicing, and so on. What once looked like a particulate gene now turns out to be scattered across parts of the genome with no hard-and-fast boundaries. Genes seem to depend on the genome's regulatory activities which, in turn, may depend on how the molecular biologist wishes to manipulate the genome in experiment. This has led to the widespread opinion that the gene is devoid of any special reality, or, is just a word. I contest this view and continue to argue for a unified gene concept. I do so by defining the gene as the genetic underpinning of the smallest possible difference in adaptation that may be detected by natural selection. Differences in adaptation among individuals, by directing natural selection toward the genetic underpinning of such differences, may be instrumental in the formation of genes.

Everybody knows about genes. One can read about them in the press. Often we are told that genes are selfish and help themselves rather than the bodies they are housed in. Genes play their role in the nature/nurture debate and in health care. Also, there is an urgent need to conserve the biodiversity around us for future generations that has, of course, to do with genes. There is a big science industry of genome sequencing that is an inventory-taking of all of man's (and other organisms') DNA. Darwin searched a lifetime in vain for the hereditary units, and indeed, genes are indispensable in modern Darwinian evolutionary theory. Early this century, genes were inferred from the Mendelian behavior of traits. The year 1953 marked a breakthrough when Watson and Crick disclosed the doublestranded helical structure of DNA. This suggested an elegant explanation of how genes could replicate themselves from one generation to the next but also serve the purpose of building an individual organism in each generation. Henceforth, the gene came to be viewed as a piece of DNA that coded for a protein or, more generally, a functional or structural product. Genes were seen as inviolable messages passed down the generations (save for occasional mutations) and as the ultimate causal factors lying behind development. Once, these findings were considered evidence for one of the most successful research strategies in the life sciences during the first half of the twentieth century.