Two scientists were awarded the Nobel Prize in $2006$ for $RNA$ interference. On which organism did these scientists discover this mechanism?

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

Match Column-$I$ with Column-$II$:

Column-$I$	Column-$II$
$(i)$ Operator site	$(a)$ Codes for enzyme (protein)
$(ii)$ Promoter site	$(b)$ Codes for repressor
$(iii)$ Structural gene	$(c)$ Binding site for $RNA$ polymerase
$(iv)$ Regulator gene	$(d)$ Binding site for repressor

$Y$ gene in $lac$ operon is responsible for .....

Define an operon,give an example,and explain an inducible 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.