Gene expresses itself in a cell system as a protein/enzyme. How does an expression of gene occur in a cell system and when does it need to occur, and…

Gene expresses itself in a cell system as a protein/enzyme. How does an expression of gene occur in a cell system and when does it need to occur, and how the gene expression is regulated in a prokaryote cell system was studied by the combined efforts of Jacque Monod, the biochemist and Francois Jacob, the geneticist. For their work on lactose metabolism in E. coli and introducing the concept of "lac operon" they were awarded the Nobel Prize in 1965.

Why is lac operon said to be a transcriptionally regulated system ?

It is said that "the lac operon has to be operational at a very low level in the bacterial cell all the time." Justify.

Why is the regulator gene in lac operon marked as 'i' gene ?

Draw a schematic diagram of lac operon in absence of inducer in the culture medium of the bacteria.

Draw a schematic diagram of lac operon in the presence of inducer in the culture medium of the bacteria.