Repressible operons are operons in which the gene activity is repressed when a chemical is added.
In a repressible operon, transcription is turned off either by the repressor becoming active in a negative repressible operon or by the activator becoming inactive in a positive repressible operon.Trp operon is an repressible operon.
Inducible operons are operons in which the gene activity is induced when a chemical is added. An inducible operon requires an inducer molecule to stimulate transcription either by inactivating a repressor protein in a negative inducible operon or by stimulating the activator protein in a positive inducible operon.lac operon is an inducible operon.
The difference between repressible and inducible operons lies in the role of the effector, or molecular signal that causes a conformational change in the repressor. The effector can be either a corepressor or inducer.
If transcription is usually on but can be repressed by the binding of a corepressor to the normally inactiverepressor, the operon is referred to as a repressible operon. Transcription will decrease when the repressor is activated. Repressible operons are often used in anabolic pathways, because the end product can be a feedback inhibitor of transcription.
If transcription is normally off but can be induced by the binding of an inducer to the normally activerepressor, the operon is referred to as an inducible operon. In this way, the repressor itself is "repressed", and transcription increased. Inducible operons are often used in catabolic pathways, because the enzymes involved in catabolism do not need to be synthesized unless their substrates are present.
Apr 27th, 2015
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