Gene expresses itself in a cell system as a protein/enzyme. How an expression of gene occurs in a cell system, when it needs to occur and how the gene expression is regulated in prokaryotic cell system was studied by the combined efforts of Francois Jacob, a geneticist and Jacques Monod, a biochemist. For their work on lactose metabolism in E. coli and introducing the concept of "lac operon", they were awarded the Nobel Prize in 1965.
Why is the regulation of operon called negative regulation ?
Gene expresses itself in a cell system as a protein/enzyme. How an expression of gene occurs in a cell system, when it needs to occur and how the gene expression is regulated in prokaryotic cell system was studied by the combined efforts of Francois Jacob, a geneticist and Jacques Monod, a biochemist. For their work on lactose metabolism in E. coli and introducing the concept of "lac operon", they were awarded the Nobel Prize in 1965.
Why is the regulation of operon called negative regulation ?
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Solution and Explanation
In negative regulation a regulator protein switches the genes off, not on.
Step 2: How it applies to the lac operon:
The repressor binds the operator and blocks transcription. The operon is switched off by this repressor.
The genes can work only when the repressor is removed by the inducer.
Step 3: Conclusion:
Since the regulator acts by stopping (repressing) transcription, the control is called negative regulation.
Final Answer:
A repressor switches the operon off by binding the operator, so the control is negative.
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Gene expresses itself in a cell system as a protein/enzyme. How an expression of gene occurs in a cell system, when it needs to occur and how the gene expression is regulated in prokaryotic cell system was studied by the combined efforts of Francois Jacob, a geneticist and Jacques Monod, a biochemist. For their work on lactose metabolism in E. coli and introducing the concept of "lac operon", they were awarded the Nobel Prize in 1965.
(a) It is said that 'lac operon' has to be operational at a very low level in the bacterial cell all the time. Justify.
Gene expresses itself in a cell system as a protein/enzyme. How an expression of gene occurs in a cell system, when it needs to occur and how the gene expression is regulated in prokaryotic cell system was studied by the combined efforts of Francois Jacob, a geneticist and Jacques Monod, a biochemist. For their work on lactose metabolism in E. coli and introducing the concept of "lac operon", they were awarded the Nobel Prize in 1965.
(b) (i) How are the structural genes activated in the lac operon in E. coli ?
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