MCQ on lac and trp Operon




The lac operon and trp operon are genetic regulatory systems in prokaryotes. The lac operon controls the expression of genes responsible for lactose metabolism, allowing bacteria to use lactose as a carbon source. The trp operon regulates genes involved in tryptophan synthesis, ensuring its production when tryptophan is scarce. This MCQ on lac and trp operon will help you to understand the operon concept.

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1. 
The operon concept was proposed by:

2. 
Operons are commonly found in:

3. 
The lac operon in Escherichia coli is responsible for the metabolism of:

4. 
The lac operon is composed of the following elements:

5. 
In the absence of lactose, the lac operon is:

6. 
The lac repressor binds to the operator in the absence of lactose and prevents transcription of the structural genes. What is the allosteric effector that binds to the repressor and causes it to release the operator?

7. 
The trp operon in bacteria is responsible for the biosynthesis of:

8. 
In the absence of tryptophan, the trp operon is:

9. 
The trp repressor binds to the operator in the absence of tryptophan and prevents transcription of the structural genes. What is the corepressor that binds to the repressor and facilitates its binding to the operator?

10. 
The lac operon is under positive control by:

11. 
In the presence of both glucose and lactose, the lac operon is:

12. 
The lac operon is an example of a/an ______ operon, which is usually off and needs to be turned on.

13. 
The trp operon is an example of a/an ______ operon, which is usually on and needs to be turned off.

14. 
Which of the following operons exhibits negative control?

15. 
Mutations in the lacI gene, which codes for the lac repressor, can lead to a constitutive expression of the lac operon, even in the absence of lactose. What is such a mutant called?

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