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Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance1 Mark
MCQ
For question, two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion : Synthesis of tryptophan is self regulatory.
Reason: Tryptophan works both as co$-$repressor and through feedback inhibition.
  • ✓
    Both assertion and reason are true, and reason is the correct explanation of assertion.
  • B
    Both assertion and reason are true, but reason is not the correct explanation of assertion.
  • C
    Assertion is true, but reason is false.
  • D
    Both assertion and reason are false
✓

Answer

Correct option: A.
Both assertion and reason are true, and reason is the correct explanation of assertion.
Tryptophan regulates its own active synthesis by regulating the expression of its gene via feedback mechanism and also by acting as co$-$repressor which attaches with repressor proteins produced by regulator gene and blocking the promotor gene site thus blocking $\text{m-RNA}$ synthesis and further steps. It is thus obvious that the synthesis of tryptophan is self regulatory, since it, when present in plenty, work firstly by feedback inhibition, and secondly through co$-$repression to stop further synthesis of tryptophan.

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