Which of the following switches off the $lac$ operon?

Which enzyme is the expression product of the $y$ gene in the $lac$-operon?

Which of the following is not produced by $E. coli$ in the lactose operon?

Match List-$I$ with List-$II$.

List-$I$	List-$II$
$A$. Gene $a$	$I$. $\beta$-galactosidase
$B$. Gene $y$	$II$. Transacetylase
$C$. Gene $i$	$III$. Permease
$D$. Gene $z$	$IV$. Repressor protein

Choose the correct answer from the options given below:

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?

In the $lac$ operon,which enzyme$(s)$ will be produced in the cell if there is a nonsense mutation in the $lac$ $y$ gene?