Select the molecule/s which cannot act as inducer in Lac operon.

Options

A. Glucose
B. Lactose
C. Galactose
D. Both (1) and (3)

Answer

To solve the question about which molecule cannot act as an inducer in the lac operon, we will follow these steps:

### Step 1: Understand the Lac Operon
The lac operon is a genetic system found in E. coli that is responsible for the metabolism of lactose. It consists of genes that encode proteins necessary for the uptake and breakdown of lactose into glucose and galactose.

**Hint:** Remember that the lac operon is inducible, meaning it can be turned on in the presence of an inducer.

### Step 2: Identify the Role of Inducers
In the lac operon, an inducer is a molecule that binds to the repressor protein, causing it to change shape and detach from the operator region of the operon. This allows RNA polymerase to access the promoter and initiate transcription of the genes required for lactose metabolism.

**Hint:** Inducers are crucial for inactivating the repressor protein in the lac operon.

### Step 3: Recognize the Inducers
The primary inducer of the lac operon is allolactose, which is an isomer of lactose. When lactose is present, it is converted into allolactose, which then binds to the repressor protein.

**Hint:** Focus on the molecules that can bind to the repressor and allow transcription to occur.

### Step 4: Identify Molecules that Cannot Act as Inducers
The question specifically asks for molecules that cannot act as inducers. In this context, glucose and galactose do not serve as inducers for the lac operon. While they are products of lactose metabolism, they do not bind to the repressor protein to activate the operon.

**Hint:** Consider the metabolic products of lactose and their roles in the lac operon.

### Step 5: Conclusion
Based on the understanding of the lac operon and the role of inducers, the molecules that cannot act as inducers in the lac operon are glucose and galactose.

**Final Answer:** Glucose and galactose cannot act as inducers in the lac operon.