Question

If a gene is repressible and under positive control, what kind of effector molecule and regulatory protein are involved in its regulation? Explain how the binding of the effector molecule affects the regulatory protein.

Short answer

In the case of a repressible gene under positive control, the effector molecule is a co-repressor and the regulatory protein involved is an activator. When the co-repressor binds to the activator, it inhibits the activator's run in enhancing the gene transcription process, hence repressing it.

Step-by-step solution

Understanding key terms

At first, it's essential to understand what is meant by a repressible gene and positive control. A repressible gene is one that usually expresses and produces a protein unless it is repressed. Positive control, on the other hand, means that the process of transcription is activated by a regulatory protein binding to DNA.

Identifying the effector molecule and regulatory protein

In the case of a repressible gene under positive control, the effector molecule would be a co-repressor and the regulatory protein would be an activator. Co-repressor is the molecule that binds the activator protein, reducing its ability to promote transcription. The activator protein is the regulatory protein that binds to DNA and aids in transcribing the gene.

Explaining the impact of effector molecule binding

When the co-repressor (effector molecule) binds to the activator (regulatory protein), it inhibits its ability to enhance the transcription process. Since this is a repressible gene and, the gene, under normal conditions, transcribes and translates, the process prevails unless it's repressed. This repression takes place when the co-repressor binds with the activator inhibiting further gene transcription.