Chapter 17 - Chapter 17: Control of Gene Expression in...

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Chapter 17: Control of Gene Expression in Bacteria E. coli have over 4,300 genes If all of those genes were expressed at the fastest possible rate at all times, the E coli. Cells would stagger off the stage Gene expression occurs when a protein or other gene product is synthesized and is active in the cell Bacteria are the most abundant organisms on Earth, and they occupy virtually every habitat known o Bacteria cells are able to grow and reproduce successfully because they respond rapidly to dramatic changes in temperature, pH, light, competitors, and nutrients o Changes in gene expression give bacteria the ability to cope with these types of environmental change Bacterial gene expression have enormous practical significance o Bacterial cells are also used commercially to manufacture important products such as human insulin and growth hormone o Efficient use of bacteria depends on a solid understanding of how transcription and translation are regulated 17.1: Gene Regulation and Information Flow: o How does a bacterial cell turn some genes on and others off so tat it can take advantage of alternative food sources? E. coli Can use a wide array of carbohydrates to supply the carbon and energy they need Precise control of gene expression gives E. coli the ability to respond to these changes in it environment and use the different sugars Bacteria can be packed an inch thick along your intestinal walls It would be energetically wasteful for E. coli to produce all of the enzymes required to process all of the various carbohydrates all of the time It is logical to predict that the enzymes being produced match the sugars that are available at a given time Efficient use of resources, via tight control over gene expression, is critical if cells are going to be able to compete successfully for space and nutrients Each type of food contains different sugars Each sugar should induce a different response by the E. coli cells Cells need to regulate which proteins they produce at any given time o Mechanism of Regulation-An Overview Gene expression can be controlled at any step between the synthesis of RNA and the activation of the final gene product Three steps occur as information flows from DNA to proteins DNA mRNA protein activated protein o First arrow, transcription Making of mRNA o Second arrow, translation Ribosomes read the information in mRNA and use that information to synthesize a protein o Third arrow, post-translational modifications Folding, addition of carbohydrate or lipid groups, or phosphorylation How can a bacteria cell conserve ATP and amino acids by avoiding the production of proteins that are not needed at a particular time? The cell could avoid making the mRNAs for particular enzymes
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Chapter 17 - Chapter 17: Control of Gene Expression in...

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