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

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
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
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
/Review/