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16: Transcriptional Regulation (prokaryotes)

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    • 16.1: The lac Operon
      Early insights into mechanisms of transcriptional regulation came from studies of E. coli by researchers Francois Jacob & Jacques Monod. In E. coli, and many other bacteria, genes encoding several different proteins may be located on a single transcription unit called an operon. The genes in an operon share the same transcriptional regulation, but are translated individually. Eukaryotes generally do not group genes together as operons (exception is C. elegans and a few other species).
    • 16.2: The Use of Mutants to Study the lac Operon
      The lac operon and its regulators were first characterized by studying mutants of E. coli that exhibited various abnormalities in lactose metabolism.
    • 16.3: Gene Regulation in Prokaryotes
      Many prokaryotic genes are organized in operons, linked genes transcribed into a single mRNA encoding two or more proteins. Operons usually encode proteins with related functions. Regulating the activity of an operon (rather than multiple single genes encoding single proteins) allows better coordination of the synthesis of several proteins at once. In E. coli, the regulated lac operon encodes three enzymes involved in the metabolism of lactose (an alternative nutrient to glucose).