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Select the two correct statements out of the four $(i-iv)$ given below about lac operon.
$i.$ 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.
$(ii)\; and\; (iii)$
$(i)\; and \;(iii)$
$(ii)\; and\; (iv)$
$(i)\; and\; (ii)$
Solution
Jacob and Monod proposed the lac operon of $E. coli.$ The lac operon contains a promoter, an operator, and three structural genes called $\mathrm{Z}, \mathrm{Y}$, and $\mathrm{A}$, coding for the enzyme, $b$ 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.
