BIOL-UA 11 Chapter : Regulation of Gene Expression
Document Summary
Natural selection favors bacteria that express only the genes whose products are needed. E. coli needs tryptophan; when the human host does not consume tryptophan, e. coli can switch to another metabolic pathway and produce tryptophan from another compound. Metabolic control occurs on two levels: enzymatic activity cells can adjust the activity of enzymes already present. Fairly fast response: relies on the sensitivity of many enzymes to chemical cues that increase or decrease their catalytic activity. Feedback inhibition allows cells to adapt to short-term fluctuations in nutrition supplies: enzyme production cells can regulate the expression of the genes encoding the enzymes. Operons: many genes of the bacterial genome are switched on or off by changes in the metabolic status of the cell. Advantage of grouping genes of related function into one transcription unit: a single on- off switch can control the whole cluster of functionally related genes (they are coordinately controlled)
