1. Tardigrade
  2. Question
  3. Biology
  4. Which of the following statements concerning the regulatory genes (R), associated with the lac operon are incorrect? I. m RNA is transcribed from the R gene whether lactose is present or not. II. m RNA is transcribed from the R gene only when the lactose is present. III. m RNA is transcribed from the R gene only when the lactose is not present. IV. Lactose inhibits the translation of R gene m RNA.

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. Which of the following statements concerning the regulatory genes (R), associated with the lac operon are incorrect?
I. $m$ RNA is transcribed from the $R$ gene whether lactose is present or not.
II. $m$ RNA is transcribed from the $R$ gene only when the lactose is present.
III. $m$ RNA is transcribed from the $R$ gene only when the lactose is not present.
IV. Lactose inhibits the translation of $R$ gene $m$ RNA.

Molecular Basis of Inheritance

Solution:

Statement II, III and IV are incorrect and only statement I is correct.
This can be explained as in lac operon model, regulatory gene is continuously working, whether lactose (inducer) is present or not. It transcribes $m RNA$ which codes for repressor.
When this repressor binds with lactose (inducers) it inhibits translation of operator gene (not R gene).
Thus, lactose presence affects operator gene not $R$ gene.