In an operon, the regulator and operator genes are notassociated with the constitutive genes.Reason (R) : Constitutive genes need not be repressed.(a) Both Assertion (A) and Reason (R) are true and Reason (R) is thecorrect explanation of the Assertion (A).(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is notthe correct explanation of the Assertion (A).(c) Assertion (A) is true, but Reason (R) is false.(d) Assertion (A) is false, but Reason (R) is true.
Question
In an operon, the regulator and operator genes are notassociated with the constitutive genes.Reason (R) : Constitutive genes need not be repressed.(a) Both Assertion (A) and Reason (R) are true and Reason (R) is thecorrect explanation of the Assertion (A).(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is notthe correct explanation of the Assertion (A).(c) Assertion (A) is true, but Reason (R) is false.(d) Assertion (A) is false, but Reason (R) is true.
Solution
The correct answer is (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
Explanation: In an operon, the regulator and operator genes are indeed not associated with the constitutive genes. This is because the regulator gene produces a repressor protein that can bind to the operator gene and prevent transcription of the structural genes. The operator gene is a segment of DNA to which the repressor binds. It is located between the promoter and the structural genes.
On the other hand, constitutive genes are genes that are always active, or "on". They are not regulated and are expressed at a fixed rate. Their activity does not need to be repressed because they are necessary for the survival of the organism. However, the fact that constitutive genes do not need to be repressed is not the reason why the regulator and operator genes are not associated with them. Therefore, while both statements are true, the reason given is not the correct explanation for the assertion.
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