Gene regulation in prokaryotes

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Gene regulation in prokaryotes[edit]

Constitutive vs Adaptive Enzymes[edit]

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[edit]

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


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

Review, Problems[edit]