Answer to Question #61081 in Genetics for Sanjukta Ghosh

Question

Is induction and derepression the same thing?

In lac operon when Allolactose molecule is present in the medium (in the bacterial cell) it binds to the monomer of repressor and reduces the binding affinity of repressor to the operator site and the RNA polymerase is free to synthesis a polycistronic mRNA. Thus the allolactose molecule turns on the expression of lac operon by removing repression.

So I conclude that in lac operon induction is same as derepression. But does it hold true for all operons or there are operons in which induction is achieved without repressing the repressor?

Answer 1

No. They are not the same. The differences between them are the following:
1. Induction:
1. It turns the operon on.
2. It starts transcription and translations.
3. It is caused by a new metabolite which needs enzymes to get metabolized.
4. It operates in a catabolic pathway.
5. Repressor is prevented by the inducer from joining the operator gene.


2. Repression:
1. It turns the operon off.
2. It stops transcription and translation
3. It is caused by an excess of existing metabolite.
4. It operates in an anabolic pathway.
5. Aporepressor is enabled by a co-repressor to join the operator gene.