What are the roles of allolactose in the lac operon and tryptophan in the trp operon?

Question

anonymous · Answer

Allolactose  is an inducer in the lac operon which binds to LacI and deactivates it.  Tryptophan on the other hand does the reverse effect. It activates the repressor TrpR by binding to it so that the genes for the Trp operon can be repressed and stopped from getting transcribed. One important thing about the Trp operon is that TrpR is not the only way by which the operon gets regulated. It is also regulated by a Leader peptide sequence. 

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