GeneRegulation160 - Gene Regulation - 1 Regulating Genes We...

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Gene Regulation - 1 Regulating Genes We have been discussing the structure of DNA and that the information stored in DNA is used to direct protein synthesis. We've studied how RNA molecules are used to transcribe and translate DNA information to direct the synthesis of specific proteins. We have also discussed briefly how mutations alter DNA sequences and can affect gene expression. We also know that each cell of an organism has exactly the same DNA, yet we have many different types of cells and tissues within a multicellular organism. For example, more than 20,000 genes have been identified in the human genome, but only a small portion of those genes are expressed in any given cell. The process of cell differentiation, in which cells become specialized for their specific function, involves selectively activating some genes and repressing others. Many genes in multicellular organisms are activated only at one stage of development, do their job, and function no more. The effects of these genes are not reversible. How does a cell " "know" what DNA is needed and when? What controls gene activity? Finding answers to these questions is the subject of gene regulation. Some of the answers to how genes are regulated are coming from work on recombinant DNA research, some from genetics and, in particular, from mutant strains of species. Gene regulation is a very active area of research in developmental biology, including stem cell research, the biology of aging, genetic diseases research, and cancer research. Genes are controlled chemically by molecules that interact with DNA, RNA and/or the polypeptide chains. Both hormone signal molecules and regulatory proteins have effects on gene expression. Genes can also be chemically modified to either enhance or inhibit their readability. Gene controls can be positive – inducing gene activity, or negative – repressing gene activity. Gene expression can be regulated at any step from DNA ± Transcription ± Translation to the final product's functionality and duration in the cell. Because gene regulation mechanisms were first studied in prokaryote transcription, much of what is presented deals with transcription control in both eukaryotes and prokaryotes. However, we will also look at some other ways that have been identified that regulate gene activity at the DNA level, as well as pre- and post-translation activities.
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Gene Regulation - 2 Regulating Gene Expression in Prokaryotic Transcription The early work on gene regulation was done with prokaryotes. It is easier to study activity in prokaryotes because they are less genetically complex, and absent a nucleus, the DNA is accessible to all components of the cell. Much of the research in gene regulation has been accomplished with Escherichia coli , the common intestinal bacterium. Moreover, gene expression in prokaryotes is organized into a discreet "package" the operon. Before we go too far, however, we need our vocabulary.
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GeneRegulation160 - Gene Regulation - 1 Regulating Genes We...

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