A mutation at the promoter of the regulator gene that inhibits transcription would result in the constitutive expression and transcription of a ___________________. Choose one.
a. positive inducible operon
b. negative inducible operon
c. positive repressible operon
d. activator protein
The correct answer is- A. POSITIVE INDUCIBLE OPERON
Explanation- The best example that can be cited is-the lac operon. In Lac operon, the Lac I gene is the Repressor molecule. If the gene is active(in absence c of lactose) , then there would be no transcription of the Lac structural genes. However, if lactose is present, the lac I protein changes its conformation and the transcription of the lac structural genes occur. This is what is called as Inducible operon, and lactose is the positive inducer for transcription.
Now when there is a mutation in the promoter of the repressor gene itself, the Lac I protein will not be produced and the lac operon will become a constitutive expressible operon. This is the positive inducible operon
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