Transposons can be used during which one of the following?

Wild-type $E. coli$ cells are grown in a normal medium containing glucose. They are then transferred to a medium containing only lactose as the sugar source. Which of the following changes will occur?

What does '$3$' represent in the given figure?

Match List-$I$ with List-$II$:

List-$I$	List-$II$
$a$. In lac operon $i$ gene codes for	$i$. Transacetylase
$b$. In lac operon $z$ gene codes for	$ii$. Permease
$c$. In lac operon $y$ gene codes for	$iii$. $\beta$-galactosidase
$d$. In lac operon $a$ gene codes for	$iv$. Repressor

Choose the correct answer from the options given below:

Match Column-$I$ with Column-$II$:

Column-$I$	Column-$II$
$(i)$ Operator site	$(a)$ Codes for enzyme (protein)
$(ii)$ Promoter site	$(b)$ Codes for repressor
$(iii)$ Structural gene	$(c)$ Binding site for $RNA$ polymerase
$(iv)$ Regulator gene	$(d)$ Binding site for repressor

Which of the following statements is incorrect regarding the $lac$ operon?