Question

compare and contrast the lac operon and respressible operon systems

Answer 1

Lac operon is an inducible operon and is catabolic in nature. An inducible operon is an operon in which the presence of a key metabolic substance induces transcription of the structural genes. Lac Operon codes for enzymes to metabolize lactose, so it's inactive without lactose. Inducer inactivates repressor so genes can be transcribed.

Repressible operon  is an operon which always transcribes structural genes unless a repressor is present. One example of a repressible operon is trp operon and the co-repressor of this operon is tryptophan. It is anabolic in nature. Trp Operon codes for enzymes to make trp, so its active without trp: repressible. repressor molecule activates repressor protein so genes can function.