Question

An operon is controlled by a repressor. When the repressor binds to a small molecule, it binds to DNA near the operon. The operon is constitutively expressed if a mutation prevents the repressor from binding the small molecule. This is an example of a ______________ operon.

Answer 1

Answer:

Negatively repressible.

Explanation:

A control which occurs through repressor is known as negative control which may be inducible or repressible.

When a small molecule named as allolactose binds this repressor it leads to allosteric repulsion which removes repressor from the operator as a result of which RNA polymerase can start transcription. Allolactose is therefore known as inducer because it induces lac operon expression.

But here, the operator is active (induced) already so there is no need to induce the operon which means that it can only be repressed so that transcription could stop. So the answer is negatively repressible operon.