Definitions/Explanation : Splicing & Operator gene
$(1)$ The primary transcripts contain both the exons and introns and are non-functional. Hence it is subjected to a process called splicing where introns are removed and exons are joined in a defined order.
$(2)$ It gives passage to $RNA$ polymerase moving from promotor to structural gene i.e. it control. activity of structural gene.
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.
Lac operon is
$A$ : Lac operon exerts negative control only.
$R$ : The operator is occupied by aporepressor during regulation
Which of the following switch off lac operon