Final answer:
A constitutive operon is one whose genes are transcribed and translated continuously to provide constant intermediate levels of protein products and are essential for basic cellular functions and metabolism.
Step-by-step explanation:
An operon encoding genes that are transcribed and translated continuously to provide the cell with constant intermediate levels of the protein products is said to be a constitutive operon. Constitutive operons are responsible for the expression of housekeeping genes needed for basic cellular functions and essential metabolic processes. Unlike inducible or repressible operons, such as the lac operon (which is an example of an inducible operon) or the tryptophan (trp) operon (an example of a repressible operon), constitutive operons do not require additional signals to initiate transcription.
They are unregulated because their gene products are constantly required for the survival and maintenance of the cell. In prokaryotes, constitutive operons are expressed all the time and their gene products are required consistently. They are involved in housekeeping functions like DNA replication, repair, and core metabolism. Constitutive operons are not regulated by repressors, activators, or inducers.