CBSE 2025, Compartment, Set 1

Question

Observe the diagram given below and answer the following questions.

![Lac Operon Diagram](https://www.edvaya.com/images/cbse/biology/2025/lac-operon-translation-diagram.webp)

(i) Name the molecule 'X' synthesized by 'i' gene.
(ii) Which one of the structural genes codes for $\beta$-galactosidase?
(iii) When will the transcription of this gene stop ?

Edvaya · Accepted Answer

The correct answer is Subjective. **SOLUTION** Based on the mechanics of the *lac* operon: * **(i) Molecule X:** The molecule synthesized by the regulatory '$i$' gene is the **Repressor protein**. * **(ii) Gene coding for $\beta$-galactosidase:** The structural **$z$ gene** specifically codes for the enzyme $\beta$-galactosidase. * **(iii) Termination of Transcription:** The transcription of these structural genes will promptly stop **in the absence of lactose** (the inducer), allowing the repressor protein to remain active and physically bind to the operator region.

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Biology > Reproduction And Genetics > Molecular Basis Of Inheritance

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