$$ \text{Corepressor} + \text{Inactive Repressor} \rightarrow \text{Active Repressor} $$

Question 1

Which of the following best describes the mechanism by which a repressible operon is turned 'off'?

Accepted Answer

A corepressor binds to the repressor protein, activating it so it can bind to the operator and block transcription.

Question 2

In the context of the repressible operon shown, what would happen if the corepressor was not present in the cell?

Accepted Answer

The repressor would remain inactive and the genes would be expressed.

Question 3

Which of the following equations best represents the binding interaction that leads to gene repression in a repressible operon?

Accepted Answer

$$ 	ext{Corepressor} + 	ext{Inactive Repressor} ightarrow 	ext{Active Repressor} $$

Question 4

If a mutation prevents the repressor protein from binding the corepressor, what is the most likely outcome for the operon?

Accepted Answer

The operon will remain 'on' and the genes will be continuously expressed.

Question 5

Which of the following statements about repressible operons is FALSE?

Accepted Answer

The repressor protein is always active and always bound to the operator.

Question 6

In a repressible operon, what is the role of the operator region?

Accepted Answer

It serves as the binding site for the active repressor, blocking RNA polymerase.

Question 7

Which of the following best explains why a repressible operon is considered a negative feedback system?

Accepted Answer

The end product (corepressor) inhibits further gene expression by activating the repressor.

Microbiology Exam 2 Study Guide: Genetics, Microbial Diversity, and Molecular Techniques

Study Guide - Practice Questions