Question

Inducible operons differ from repressible operons in that

• A. operator of inducible operons is switched off by a repressor protein
• B. inducible operons have an operator that controls binding of RNA polymerase to the promoter region
• C. inducible operons use activators and positive control to regulate their transcription
• D. inducible operons usually include structural genes that function in catabolic pathways

Answer 1

The correct option is D inducible operons usually include structural genes that function in catabolic pathways

The inducible operon is usually off and it can be induced in the presence of inducer like lactose. After getting induced, the operon is turned on and transcription takes place to catabolize these inducers. Hence, the inducible operon is usually involved in catabolism.

While repressible operon is on normally and results in transcription of structural genes to produce the desired product for e.g. tryptophan. Hence, it works at times when the bacterial cell does not require these products like tryptophan and the presence of tryptophan from external source turns off this operon.

So, the correct option is 'inducible operons usually include structural genes that function in catabolic pathways'.