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Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance3 Marks
Question
Where is an operator' located in a prokaryotic DNA? How does an operator regulate gene expression at transcription level in a prokaryote? Explain.
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Answer

  1. The operator' region is adjacent to the promoter region.
  2. The operator regulates the accessibility of promoter region to the RNA polymerase for transcription.
  3. The operator binds to the repressor protein coded by the regulatory gene and prevents the RNA polymerase from binding to the promoter; the operon is switched "off".
  4. When an inducer binds to the repressor and inactivates it, it cannot bind to the operator; this allows RNA polymerase access to the promoter and transcription continues, i.e., the operon is switched 'on'.

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