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The lac operon consists of a regulation ...

The lac operon consists of a regulation gene and three structural gene. The lactose acts as inducer. In the presence of an Inducer such as lactose, the repressor is in inactivated during the interaction. This allows RNA polymerase access to the promoter and transcription proceeds. The repressor is synthesized which in turn binds with the operator region of the operon and prevents RNA polymerase from transcribing the operon.
The lac operon of E. coli contains genes involved in lactose metabolism. It's expressed only when lactose is _____ (1)and glucose is _____(2).

A

1: Present, 2: Absent

B

1: Absent, 2: Present

C

1: More, 2: less

D

1: repressed, 2: promoted

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To solve the question regarding the lac operon of E. coli and the conditions under which it is expressed, we need to analyze the roles of lactose and glucose in the regulation of this operon. ### Step-by-Step Solution: 1. **Understanding the Lac Operon**: The lac operon consists of a regulatory gene and three structural genes (Z, Y, A) that are involved in lactose metabolism. The operon is controlled by a repressor that binds to the operator region, preventing transcription when lactose is absent. 2. **Role of Lactose**: Lactose acts as an inducer. When lactose is present, it binds to the repressor, inactivating it. This inactivation allows RNA polymerase to access the promoter region and initiate transcription of the structural genes necessary for lactose metabolism. 3. **Role of Glucose**: Glucose is the preferred carbon source for E. coli. When glucose is present, the lac operon is not expressed, even if lactose is available. This is because the presence of glucose inhibits the expression of the operon, as the cell prioritizes glucose utilization over lactose. 4. **Conditions for Expression**: The lac operon is expressed only when: - Lactose is **present** (inducing the operon by inactivating the repressor). - Glucose is **absent** (allowing the cell to utilize lactose as an alternative carbon source). 5. **Final Answer**: Therefore, the lac operon of E. coli is expressed only when lactose is **present** (1) and glucose is **absent** (2).
To solve the question regarding the lac operon of E. coli and the conditions under which it is expressed, we need to analyze the roles of lactose and glucose in the regulation of this operon. ### Step-by-Step Solution: 1. **Understanding the Lac Operon**: The lac operon consists of a regulatory gene and three structural genes (Z, Y, A) that are involved in lactose metabolism. The operon is controlled by a repressor that binds to the operator region, preventing transcription when lactose is absent. 2. **Role of Lactose**: Lactose acts as an inducer. When lactose is present, it binds to the repressor, inactivating it. This inactivation allows RNA polymerase to access the promoter region and initiate transcription of the structural genes necessary for lactose metabolism. ...
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