A structural gene – evolving term and dilemmas

The term “gene” was originally used as a purely theoretical concept. After discovery of DNA structure, and understanding the genetic code, the gene acquired a form of a distinct physical entity with its borders and specific signal sequences, having rather simple (as it was thought at that time) functions and relation to phenotype outcome. The term “structural gene” has been coined. The unique gene structure, and several unusual and omnipotent traits have been ascribed to the gene that resulted in the formulation of a “genocentric” theory as a basic expla nation of all features of living organisms. However, recent discoveries reveal a complex structure and functions of eukaryotic genes. It appears now that the coding sequences (exons) are spread out over extended regions (hundreds of thousands of kilobases) of DNA. The role of protein-non coding DNA sequences were recognized, and the new mechanisms controlling gene functions have been discovered. In addition, we acquired the knowledge about a powerful ability of the cell to interpret the information potential of genes, accordingly to the needs of a cell/organ or actual “context” and status of the dynamic systems operating within the cell. All these discoveries undermine the genocentric view of life. At this time any definition of “gene” seems to be inadequate with present knowledge, and one may ask again: what is a gene?