Prokaryotic Gene Regulation Quiz || Molecular Biology Quiz

1.Which of the following best describes an operon?
A sequence of DNA where RNA polymerase binds.
A regulatory protein that binds to DNA
A segment of DNA that codes for a single protein.
A cluster of genes transcribed together with their regulatory elements.

2.In the lac operon, what is the role of allolactose?
It enhances the binding of RNA polymerase to the promoter.
It acts as a corepressor, binding to the repressor protein and enabling it to bind to the operator.
It serves as an inducer, binding to the repressor protein and causing it to release from the operator.
It binds to the operator sequence, blocking RNA polymerase

3. What is the regulatory outcome of the trp operon when tryptophan levels are high?
Transcription is initiated but blocked at the operator.
Transcription is attenuated and repression occurs.
The operon is repressed but not attenuated.
Transcription is fully activated.

4. Which of the following is an example of negative gene regulation?
A small molecule, like cAMP, binds to a protein to enhance its function.
An activator protein binds to the promoter to increase transcription.
A transcription factor increases the affinity of RNA polymerase for the promoter.
A repressor protein binds to the operator to block transcription.

5.What is the function of the operator sequence in an operon?
It codes for the repressor protein
It is the binding site for a regulatory protein like a repressor.
It codes for the structural genes.
It is the binding site for RNA polymerase

6. Which of the following best describes an inducible operon?
It is only active when both glucose and lactose are absent.
It is normally on, and transcription is turned off by a repressor.
It is always transcribed, regardless of environmental conditions.
It is normally off, and transcription is turned on by a molecule called an inducer.

7. What is the effect of high glucose levels on the lac operon transcription?
It leads to high levels of cAMP, which activates the CAP protein.
It leads to low levels of cAMP, resulting in a low rate of transcription.
It directly binds to the promoter, increasing the efficiency of RNA polymerase
TIt enhances the repressor's ability to bind to the operator.

8. In the trp operon, what molecule acts as a corepressor?
Lactose
Tryptophan
Allolactose
Glucose

9.What is the primary difference between regulation of the lac operon and the trp operon?
The lac operon is only regulated by negative control, whereas the trp operon is only regulated by positive control.
The lac operon is regulated by a repressor, while the trp operon is regulated by an activator.
The lac operon regulates gene expression based on the availability of a sugar, and the trp operon regulates it based on an amino acid.
The lac operon is a repressible operon, while the trp operon is an inducible operon.

10. Catabolite repression in the lac operon is an example of positive control because:
The binding of a transcription factor (CAP) to DNA promotes transcription
The absence of glucose leads to the operon's repression.
The repressor protein is always present and binds to the operator.
The operon is only transcribed in the presence of lactose.

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