Prokaryotic Regulation Inducible/Repressible and Positive/Negative Control Syste
ID: 219630 • Letter: P
Question
Prokaryotic Regulation Inducible/Repressible and Positive/Negative Control Systems Not all genes are expressed all the time, most are expressed only when the gene product (protein) is needed. In order to control the abundance of these gene products, transcription is regulated. . Triggers - non-proteins: tells when transcription is to occur. ?Inducible System-the presence of the trigger-Ledo tums-. -transcription ?Repressible System-the presence of the trigger-muniu-tums-in-transcription Mechanisms-tells you how the DNA binding protein alters transcription >Negative System- Binding of the protein to DNA ate transcription ?Positive System . Binding of the protein to DNA-nut. transcription Positive Negative Inducer not present: Inducer not present +he Stnes hb Inducible Inducer present The 5e Switched on-etprserwith Inducer present on Corepressor not present: Corepressor not present: he Sencs Repressible Corepressor present:?heysn? 11k2 | Corerressor present:Explanation / Answer
When inducer is not present: In the absence of inducer, the repressor binds to operator and turns off the transcription.
When inducer is present; The inducer binds to operator to turn on the transcription. For example, Lac operon is inducible and allolactose is the inducer molecule.
When corepressor is not present: The repressor cannot bind to operator and the transcription of genes is turned on.
When corepressor is present: it eneables the repressor to bind to the operator and turns off the transcription o f genes. Trp operon is repressible operon and Trp gene acts as corepressor to prevent trasncription when tryprtophan is abundant.
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