Differences between inducible and repressible operon:

INDUCIBLE OPERON:

1. In inducible operon, the genes are kept switched off until a specific metabolite inactivates the repressor.
2. It operates in catabolic pathway.
3. It starts transcription and translation.
4. It is caused by a new metabolite, which needs enzymes to get metabolized. Thus, the nutrients utilized in the pathway activate enzyme synthesis.
5. Repressor is prevented by the inducer from joining the operator gene.
6. E.g., lac operon is an inducible operon.
7. Without lactose, E.coli do not produce beta-galactosidase, lactose permease, and transacetylase. When lactose is added to the medium, E.coli start producing the enzymes.

REPRESSIBLE OPERON:

1. In repressible operon, genes are kept switched on until the repressor is activated by a specific metabolite.
2. It operates in an anabolic pathway.
3. It stops transcription and translation.
4. The production is switched off by the end products of the pathway which repress enzyme synthesis. It is caused by an excess of existing molecules.
5. Apo-repressor is enabled by a co-repressor to join the operator gene.
6. E.g., trp operon is an repressible operon.
7. Without tryptophan, E.coli produce a lot of tryptophan. when tryptophan is added to the medium, E.coli stop producing tryptophan.