ABSTRACT
The regulation of gene expression in eukaryotes is based on a multistep process called cascade of regulation which reduces gradually, by a multiplicity of sequential regulative interventions operating at the level of the consecutive information carriers. The central proposition of cascade regulation concerns the existence of a regulative system based on a multiplicity of posttranscriptional controls integrated into a hierarchical order. The first phase of cascade regulation concerns transcription, or more precisely, the preconditioning of the genomic deoxyribonucleic acid (DNA) for transcription in a given cell at a given time. This process comprises at least three distinct phases. The formation of a specific genome out of the genetic pool of the species by sexual combination and interchange. The structural and/or chemical modifications of the germ line DNA to constitute the genetic package of a given individual somatic cell. Association of this DNA with carriers of positive or negative control signals.
