Question:
About 'lac operon', which of the following statements is NOT correct?
About 'lac operon', which of the following statements is NOT correct?
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Polycistronic mRNA of lac operon translates into 3 separate proteins: $\beta$-galactosidase (Z), Permease (Y), and Transacetylase (A).
Updated On: Sep 15, 2026
- It is operative in prokaryotes only
- It transcribes three adjacent structural genes together
- The transcript is translated individually for each gene
- The polypeptides of all the structural genes mix to form one functional protein
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The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
The lac operon in Escherichia coli (formulated by François Jacob and Jacques Monod) regulates lactose catabolism.
Step 2: Detailed Explanation:
The lac operon transcribes a single polycistronic mRNA encoding three adjacent structural genes: lacZ, lacY, and lacA.
This polycistronic transcript contains separate Shine-Dalgarno sequences and is translated into three independent, distinct functional enzymes:
1. $\beta$-galactosidase (encoded by lacZ)
2. $\beta$-galactoside permease (encoded by lacY)
3. $\beta$-galactoside transacetylase (encoded by lacA).
These polypeptides do NOT fuse or mix to form one single functional protein.
Step 3: Final Answer:
Therefore, statement D is NOT correct.
The lac operon in Escherichia coli (formulated by François Jacob and Jacques Monod) regulates lactose catabolism.
Step 2: Detailed Explanation:
The lac operon transcribes a single polycistronic mRNA encoding three adjacent structural genes: lacZ, lacY, and lacA.
This polycistronic transcript contains separate Shine-Dalgarno sequences and is translated into three independent, distinct functional enzymes:
1. $\beta$-galactosidase (encoded by lacZ)
2. $\beta$-galactoside permease (encoded by lacY)
3. $\beta$-galactoside transacetylase (encoded by lacA).
These polypeptides do NOT fuse or mix to form one single functional protein.
Step 3: Final Answer:
Therefore, statement D is NOT correct.
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