Question

What is the difference between a repressible and an inducible operon?

a) Repressible operons are always active, while inducible operons are inactive.
b) Repressible operons are controlled by end-product concentration, while inducible operons are regulated by substrate presence.
c) Inducible operons produce repressor proteins, while repressible operons produce inducers.
d) Inducible operons produce end products, while repressible operons produce substrate molecules.

Answer 1

Repressible operons are active by default and produce enzymes needed for biosynthetic pathways, but are turned off when the end product accumulates. Inducible operons are inactive by default and are only activated in the presence of a specific substrate.

Step-by-step explanation:

Repressible and inducible operons are two types of operons that regulate gene expression in prokaryotic cells. Repressible operons, like the trp operon, are typically active and produce the enzymes needed for a biosynthetic pathway. However, when the end product of the pathway accumulates and is no longer needed, the operon is turned off through the action of a repressor protein. On the other hand, inducible operons, like the lac operon, are inactive by default and are only activated when a specific substrate is present. The presence of the substrate leads to the activation of gene expression through the action of an inducer molecule.