The gene concept has played a central role in Biology since its introduction, in the beginnings of the twentieth century. However, throughout its historical development, this concept has been a matter of increasing controversy, initially in the philosophy of biology and, later, in biology itself. Challenges to the gene concept have resulted in the difficulty of preserving the so called classical molecular concept, according to which a gene is a stretch of DNA encoding a functional product (polypeptide or RNA). The last three decades of experimental studies led to findings such as interrupted genes, alternative splicing, so called junk DNA, TAR sequences, pseudogenes, postranscriptional regulation, RNAi and RNAsi, among others, that posed unexpected difficulties to the usual understanding of the gene concept. In this paper, we address the main experimental findings that challenge the classical molecular gene concept. We focus, in particular, on recent advances that took place in the Human Genome Project (hgp) and the Encyclopedia of DNA elements (Encode). It is now clear for that a careful analysis and reformulation of this central concept for biological thought is necessary. In an attempt to organize the variety of definitions given to genes, many philosophers and scientists presented interesting views about this concept and its role in biological thought, as well as proposals of conceptual revision, which we will also discuss in this paper. We conclude that a single, all-encompassing definition of gene is neither possible nor necessary. Rather, a pluralism of models and concepts is likely to be more powerful, provided that the domains of each concept or model be clearly defined.
Classical molecular concept; Challenges; Human Genome Project; Encode
