In the $lac$ operon concept of gene expression,allolactose acts as:

What is the correct sequence of structural genes in the $lac$ operon?

Consider the following statements of gene regulation and select the correct statements $:$
$(A)$ Expression of genes is regulated by metabolic,physiological,or environmental conditions.
$(B)$ Galactose can act as an inducer for the lac operon.
$(C)$ The operator region is adjacent to the promoter elements in most operons.
$(D)$ In the lac operon,lactose is transported into the cell through the action of permease.
$(E)$ Regulation of the lac operon by a repressor is referred to as positive regulation.

The equivalent of a structural gene is

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

$A$ gene that is responsible for the synthesis of a polypeptide chain is called a .......