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

Select two correct statements from the four $(a-d)$ given below regarding the $lac$ operon.
$(A)$ Glucose or galactose may bind with the repressor gene and induce inactivity.
$(B)$ In the absence of lactose,the repressor binds with the operator region.
$(C)$ The $z$-gene codes for permease.
$(D)$ This was elucidated by Francois Jacob and Jacques Monod.
Which of the following are the correct statements?

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 accessibility of promoter regions of bacterial $DNA$ in many cases is regulated by the interaction of proteins with sequences termed:

Define the following terms: Regulator gene and Promoter gene.