Gene regulation in prokaryotes

Readings

• Study guide:
• Wikipedia article: Operon
• Wikipedia article: The Lac Operon
• Wikipedia article: The Arabinose Operon
• Wikipedia article: The Tryptophan Operon

Gene regulation in prokaryotes

Main resources: Gene regulation and prokaryotes

Constitutive vs Adaptive Enzymes

Genes for constitutive enzymes are always on and the gene is always produced. Adaptive genes may be either inducible (generally off; may be turned on) or repressible (generally on; may be turned off).

Adaptive enzymes

Main resources: Gene regulation and prokaryotes

Inducible Genes are generally enzymes necessary for catabolism and are only turned on if substrate is present as the substrate acts an inducer (effector).

e.g. The lac operon, The ara operon

Repressible Genes are generally enzymes involved in anabolism and are inhibited by feedback (the end product acts as a repressor for the gene)

e.g. Trp operon

Operons

Main resource: Operons

An operon is a group of genes that are coregulated. These genes usually have related function and are often cotranscribed as a single mRNA strand. Such an RNA strand is called a Polycistronic RNA

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