CONSTRUCTION OF THE DEVELOPMENTAL GENE CONCEPT - THE CRUCIAL YEARS - 1960-1980

In 1961, FRANCOIS JACOB and JACQUES MONOD proposed a model for the mec hanisms regula ting gene expression in bacteria, called the operon mod el, which was immediately enlarged by its authors to explain cellular differentiation. By suggesting that the control of embryogenesis resul ted from the action of a hierarchy of regulator genes, this model cons tituted an attempt to fill the gap between genetics and embryology whi ch had existed since the beginning of the century. After a short perio d of enthusiasm, the interest of this model was questioned. The molecu lar mechanisms at work in higher organisms seemed to be different from those operating in microorganisms. Moreover, the possibility of expla ining at the genetic level the phenomenon of cell determination was re jected. However, between 1970 and 1980, groups of Drosophila geneticis ts established that a family of genes, called selector genes, was invo lved in cell determination and responsible for the formation of cell c ompartments during embryogenesis. After 1980, the tools of genetic eng ineering allowed the isolation and characterization of these developme ntal genes.