Compare and contrast the lactose operon with the tryptophan operon

Question

What will be an ideal response?

Answer 1

Both the lactose and the tryptophan operons have certain features in common. They both contain a set of genes dedicated to a common purpose (such as the catabolism of lactose by the genes of the lactose operon) and regulatory elements such as a promoter and an operator. Each of these operons makes use of a repressor protein, which binds to the operator region and alters the activity of the operon. However, the lactose operon is classified as an inducible operon, which means it requires an inducer (a lactose metabolite) in order to be activated. In the absence of the inducer, the repressor protein shuts down the operon. In contrast, the tryptophan operon is a repressible operon, which requires a corepressor (tryptophan itself) in order to activate the repressor and shut down the operon. In the absence of the corepressor and repressor, the operon is fully functional. In both types of operons, the molecule either catabolized (in the case of lactose) or synthesized (in the case of tryptophan) is an important component of the regulation of the operon. In this way, the cell maintains precise control over these genetic pathways and does not spend time and energy making enzymes that are not needed. For example, making enzymes to catabolize lactose when no lactose is present would waste energy and metabolites.