Final answer:
An operon is a unit of genetic expression in prokaryotic cells, like bacteria, which includes genes and controlling sequences. Operons are subject to various regulatory controls including inducible, repressible, and activator control, which determine whether the genes are transcribed. The lac operon is a key example that regulates lactose metabolism in bacteria.
Step-by-step explanation:
The question asks if I can match operons to their definitions. An operon is a unit of genetic expression in prokaryotic cells, consisting of one or more related genes and the sequences controlling them, which include the operator, promoter, and sometimes, a regulatory gene. The lac operon is an example that regulates lactose metabolism.
Operons can be controlled through inducible control, repressible control, and activator control. Inducible operons require an inducer to remove a repressor for transcription to occur, while repressible operons can be switched off by the product of their gene pathway. Activator control involves a substance that must bind to the promoter region to enhance the affinity of RNA polymerase to the promoter.
In the lac operon, in the presence of lactose, a molecule of lactose binds to the repressor, changing its shape and preventing its binding to the operator. This allows RNA polymerase to bind the promoter and transcribe the genes required for lactose metabolism.