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Which of the following statements is INCORRECT for lac operon system in E. coli?
- a)It has three structural genes Z, Y, A
- b)cAMP-CAP exerts a negative regulatory effect on lac operon
- c)Repressor bound to operator site does not allow expression of lac operon
- d)Mutation of operator region lac O- results in constitutive synthesis of the enzymes.
Correct answer is option 'B'. Can you explain this answer?
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Which of the following statements is INCORRECT for lac operon system i...
Catabolite activator protein (CAP) acts as a glucose sensor. It activates transcription of the operon, but only when glucose levels are low. CAP senses glucose indirectly, through the “hunger signal” molecule cAMP, whereby a CAP-cAMP complex is recruited to the promoter site. Therefore, they exert a positive regulatory effect on lac operon.
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Which of the following statements is INCORRECT for lac operon system i...
Introduction:
The lac operon system in E. coli is a well-studied example of gene regulation in prokaryotes. It consists of three structural genes (Z, Y, A) encoding enzymes involved in lactose metabolism, as well as regulatory elements that control the expression of these genes. The lac operon can be induced in the presence of lactose, and its regulation involves the binding of specific proteins to operator and promoter regions.
Statement:
cAMP-CAP exerts a negative regulatory effect on lac operon.
Explanation:
The statement is incorrect. cAMP-CAP (cyclic AMP-catabolite activator protein) exerts a positive regulatory effect on the lac operon, not a negative one.
Positive regulation by cAMP-CAP:
- In the absence of lactose, the lac operon is usually repressed by the lac repressor protein, which binds to the operator site and prevents transcription of the structural genes.
- However, when lactose is present, it is converted into allolactose, which acts as an inducer. Allolactose binds to the lac repressor, causing a conformational change and releasing it from the operator site.
- In addition to allolactose, the lac operon requires the presence of cAMP-CAP for full induction. cAMP is a small molecule that accumulates when glucose levels are low.
- The cAMP-CAP complex binds to a specific site called the CAP site, located upstream of the promoter. This binding enhances the binding of RNA polymerase to the promoter, leading to increased transcription of the lac operon genes.
Negative regulation by lac repressor:
- The lac repressor protein encoded by the lacI gene binds to the operator site under non-inducing conditions and prevents RNA polymerase from transcribing the structural genes.
- This binding of the lac repressor to the operator site is facilitated by the absence of lactose or allolactose.
- When lactose or allolactose is present, it binds to the lac repressor and induces a conformational change, causing the repressor to dissociate from the operator site and allowing transcription to occur.
Conclusion:
In summary, the lac operon system in E. coli is regulated by both positive and negative mechanisms. The statement that cAMP-CAP exerts a negative regulatory effect on the lac operon is incorrect. cAMP-CAP actually plays a positive role in the induction of the lac operon by enhancing the binding of RNA polymerase to the promoter.
The lac operon system in E. coli is a well-studied example of gene regulation in prokaryotes. It consists of three structural genes (Z, Y, A) encoding enzymes involved in lactose metabolism, as well as regulatory elements that control the expression of these genes. The lac operon can be induced in the presence of lactose, and its regulation involves the binding of specific proteins to operator and promoter regions.
Statement:
cAMP-CAP exerts a negative regulatory effect on lac operon.
Explanation:
The statement is incorrect. cAMP-CAP (cyclic AMP-catabolite activator protein) exerts a positive regulatory effect on the lac operon, not a negative one.
Positive regulation by cAMP-CAP:
- In the absence of lactose, the lac operon is usually repressed by the lac repressor protein, which binds to the operator site and prevents transcription of the structural genes.
- However, when lactose is present, it is converted into allolactose, which acts as an inducer. Allolactose binds to the lac repressor, causing a conformational change and releasing it from the operator site.
- In addition to allolactose, the lac operon requires the presence of cAMP-CAP for full induction. cAMP is a small molecule that accumulates when glucose levels are low.
- The cAMP-CAP complex binds to a specific site called the CAP site, located upstream of the promoter. This binding enhances the binding of RNA polymerase to the promoter, leading to increased transcription of the lac operon genes.
Negative regulation by lac repressor:
- The lac repressor protein encoded by the lacI gene binds to the operator site under non-inducing conditions and prevents RNA polymerase from transcribing the structural genes.
- This binding of the lac repressor to the operator site is facilitated by the absence of lactose or allolactose.
- When lactose or allolactose is present, it binds to the lac repressor and induces a conformational change, causing the repressor to dissociate from the operator site and allowing transcription to occur.
Conclusion:
In summary, the lac operon system in E. coli is regulated by both positive and negative mechanisms. The statement that cAMP-CAP exerts a negative regulatory effect on the lac operon is incorrect. cAMP-CAP actually plays a positive role in the induction of the lac operon by enhancing the binding of RNA polymerase to the promoter.
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Which of the following statements is INCORRECT for lac operon system inE. coli?a)It has three structural genes Z, Y, Ab)cAMP-CAP exerts a negative regulatory effect on lac operonc)Repressor bound to operator site does not allow expression of lac operond)Mutation of operator region lac O- results in constitutive synthesis of the enzymes.Correct answer is option 'B'. Can you explain this answer?
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Which of the following statements is INCORRECT for lac operon system inE. coli?a)It has three structural genes Z, Y, Ab)cAMP-CAP exerts a negative regulatory effect on lac operonc)Repressor bound to operator site does not allow expression of lac operond)Mutation of operator region lac O- results in constitutive synthesis of the enzymes.Correct answer is option 'B'. Can you explain this answer? for IIT JAM 2024 is part of IIT JAM preparation. The Question and answers have been prepared according to the IIT JAM exam syllabus. Information about Which of the following statements is INCORRECT for lac operon system inE. coli?a)It has three structural genes Z, Y, Ab)cAMP-CAP exerts a negative regulatory effect on lac operonc)Repressor bound to operator site does not allow expression of lac operond)Mutation of operator region lac O- results in constitutive synthesis of the enzymes.Correct answer is option 'B'. Can you explain this answer? covers all topics & solutions for IIT JAM 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Which of the following statements is INCORRECT for lac operon system inE. coli?a)It has three structural genes Z, Y, Ab)cAMP-CAP exerts a negative regulatory effect on lac operonc)Repressor bound to operator site does not allow expression of lac operond)Mutation of operator region lac O- results in constitutive synthesis of the enzymes.Correct answer is option 'B'. Can you explain this answer?.
Which of the following statements is INCORRECT for lac operon system inE. coli?a)It has three structural genes Z, Y, Ab)cAMP-CAP exerts a negative regulatory effect on lac operonc)Repressor bound to operator site does not allow expression of lac operond)Mutation of operator region lac O- results in constitutive synthesis of the enzymes.Correct answer is option 'B'. Can you explain this answer? for IIT JAM 2024 is part of IIT JAM preparation. The Question and answers have been prepared according to the IIT JAM exam syllabus. Information about Which of the following statements is INCORRECT for lac operon system inE. coli?a)It has three structural genes Z, Y, Ab)cAMP-CAP exerts a negative regulatory effect on lac operonc)Repressor bound to operator site does not allow expression of lac operond)Mutation of operator region lac O- results in constitutive synthesis of the enzymes.Correct answer is option 'B'. Can you explain this answer? covers all topics & solutions for IIT JAM 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Which of the following statements is INCORRECT for lac operon system inE. coli?a)It has three structural genes Z, Y, Ab)cAMP-CAP exerts a negative regulatory effect on lac operonc)Repressor bound to operator site does not allow expression of lac operond)Mutation of operator region lac O- results in constitutive synthesis of the enzymes.Correct answer is option 'B'. Can you explain this answer?.
Solutions for Which of the following statements is INCORRECT for lac operon system inE. coli?a)It has three structural genes Z, Y, Ab)cAMP-CAP exerts a negative regulatory effect on lac operonc)Repressor bound to operator site does not allow expression of lac operond)Mutation of operator region lac O- results in constitutive synthesis of the enzymes.Correct answer is option 'B'. Can you explain this answer? in English & in Hindi are available as part of our courses for IIT JAM.
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