• Regulation of transcription in prokaryotes typically involves operons.
  • An operon is a region of DNA that consists of one or more genes that encode the proteins needed for a specific function.
  • A well-known example of operon regulation involves the lac operon in E. coli bacteria.
  • The Lac operon consists of a promoter, an operator, and three genes.
  • The genes are expressed only in the presence of lactose, the sugar found in milk.
  • When lactose is absent, a repressor protein binds to the operator.
  • This blocks the binding of RNA polymerase to the promoter.
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