Question

Select the two correct statements out of the four (a-d) given below about lac operon
(a) Glucose or galactose may bind with the repressor and inactivated
(b) In the absence of lactose the repressor binds witht the operator region
(c) The z-gene codes for permease
(d) This was elucidated by Francois Jacob and Jacque Monod
The correct statements are

• A. (b) and (d)
• B. (a) and (b)
• C. (b) and (c)
• D. (a) and (c)

Answer 1

The correct option is A (b) and (d)

In lac operon, lactose acts as the inducer that binds with the repressor and inactivates it. This enables the operator to carry out the translation of the genes and produce enzymes. If glucose is present in the system there is no need of lac operon as it is the preferred substrate. Since galactose is not an inducer it cannot bind with the repressor.

In the absence of lactose repressor binds with the operator and does not allow translation of the genes and hence no enzymes will be formed.

The lac z gene codes for galactosidase enzyme. Permease is encoded by lac y gene.

So, the correct option is '(b) and (d)'.