Define the following terms: Regulator gene and Promoter gene.

Transposons can be used in which of the following processes?

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

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

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.

In $lac$ operon,$z$ gene codes for: