7.4 Gene Expression

Operons

• Genes can be turned on/off according to conditions in the cellular environment.

• Genes that are functionally related to one another are grouped into clusters called operons.

Lac Operon

• Cluster of 3 genes involved in lactose metabolism.

• Consist of these genes plus:

  • Promoter - site where transcription starts.

  • Operator - regulates transcription.

  • Repressor - protein (lacI or lac repressor) that turns off genes based on lactose concentration, always produced