Question

In the operon concept, the regulator gene produces
A. Repressor
B. Inducer
C. Allolactose
D. All of the above

Answer 1

Hint: Operon Theory is the concept of gene regulation proposed by Francois Jacob and Jacques Monod.
An operon is a group of structural genes whose expression is coordinated by an operator.

Complete answer: An operon is made up of 3 basic DNA components- promoter, operator and structural genes.
1. The promoter is a nucleotide sequence that enables a gene to be transcribed.
The promoter is recognized by RNA polymerase, which then initiates transcription.
2. The operator is a segment of DNA to which a repressor bind. It is classically defined in the lac operon as a segment between the promoter and the genes of the operon.
3. In the case of a repressor, the repressor protein physically obstructs the RNA polymerase from transcribing the genes. The repressor encoded by a regulatory gene binds to the operator and represses the transcription of the operon.
4. In the presence of an inducer, the repressor is inactivated and dissociates from the operator to express the operon.
5. Thus, the expression of the operon is controlled by a cis-acting operator and by a trans-acting repressor.
6. A structural gene is a gene that codes for any RNA or protein product other than a regulatory factor.

So, the answer is A. Repressor

Note: In RNA synthesis, promoters indicate which genes should be used for messenger RNA creation and, by extension, control which proteins the cell produces.