The end product of a metabolic pathway binds to the operator to make it more active,so that it can easily bind with the repressor. In this case,the end product is called a/an ......

In the $lac$ operon,the $lac$ $mRNA$:

What are promoter,operator,and structural genes?

Lac operon is:

What does the given figure represent?

An organism is able to survive on a culture medium containing nutrient $A$ through an enzyme-catalyzed process: $A \xrightarrow{X} B \xrightarrow{Y} C$. $A$ mutant organism fails to survive on this medium. However,it grows when nutrient $B$ is added to the medium. Which gene of this mutant is defective?