Which gene produces the lactose repressor?

In $lac$ operon,the gene '$i$' codes for repressor protein,the letter '$i$' indicates . . . . . . .

$Y$ gene in $lac$ operon is responsible for .....

$A$: Operator gene is functional when it is not blocked by repressor.
$R$: Regulator gene produces active protein only which acts on operon system in $E. coli$.

Differentiation of organs and tissues in a developing organism is associated with:

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