基因组2-12 基因组活性的调控.doc

12. Regulation of Genome ActivityLearning outcomes When you have read Chapter 12, you should be able to: Distinguish between differentiation and development, and outline how regulation of genome expression underlies these two processes Describe, with examples, the various ways in which extracellular signaling compounds can bring about transient changes in genome activity, making clear distinction between those signaling compounds that enter the cell and those that bind to a cell surface receptor Describe, with examples, the various ways in which permanent and semipermanent changes in genome activity can be brought about, making clear distinction between those processes that involve rearrangement of the genome, those that involve changes in chromatin structure, and those that involve feedback loops Discuss how studies of sporulation in Bacillus subtilis, vulva development in Caenorhabditis elegans, and embryogenesis in Drosophila melanogaster have contributed to our understanding of genome regulation during development, and explain why lower organisms can act as models for development in higher eukaryotes such as humans we have followed the pathway by which expression of the genome specifies the content of the proteome, which in turn determines the biochemical signature of the cell. In no organism is this biochemical signature entirely constant. Even the simplest unicellular organisms are able to alter their proteomes to take account of changes in the environment, so that their biochemical capabilities are continually in tune with the available nutrient supply and the prevailing physical and chemical conditions. Cells in multicellular organisms are equally responsive to changes in the extracellular environment, the only difference being that the major stimuli include hormones and growth factors as well as nutrients. The resulting transient changes in genome activity enable the proteome to be remodeled continuously to satisfy the demands that the outside world p