The equivalent of a structural gene is

An $E. coli$ cell with a mutated $z$ gene of the $lac$ operon cannot grow in a medium containing only lactose as the source of energy because:

Jacob and Monod studied lactose metabolism in $E. coli$ and proposed the operon concept,which is applicable for:

In the $lac$ operon,the $lac$ $mRNA$:

The functional complex that consists of a cluster of genes including structural genes,a promoter gene,an operator gene,and a regulator gene was discovered by:

In the $lac$ operon system,the $lac$ gene-$I$ codes for: