Molecular Basis of Inheritance Question 129
129. Select the two correct statements out of the four (a-d) given below about lac operon.
[2010]
(i) Glucose or galactose may bind with the repressor and inactivate it
(ii) In the absence of lactose the repressor binds with the operator region
(iii) The $z$-gene codes for permease
(iv) This was elucidated by Francois Jacob and Jacque Monod
(a) (ii) and (iii)
(b) (i) and (iii)
(c) (ii) and (iv)
(d) (i) and (ii)
Show Answer
Answer : c
Hints & Solution
(c) Jacob and Monod proposed the lac operon of $E$. coli. The lac operon contains a promoter, an operator, and three structural genes called $z$, $y$, and $a$, coding for the enzyme, $\beta$ galactosidase, permease and transacetylase respectively. The lac regulator gene, designated as i gene, codes for repressor. In the absence of the inducer, the repressor binds to the lac operator, preventing RNA polymerase from binding to the promoter and thus transcribing the structural gene.
