In a negative operon,

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?

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

Identify the $INCORRECT$ statement with reference to the regulation of gene expression.

Human gene expression is regulated when steroid molecules bind to:

What are promoter,operator,and structural genes?