What is the arrangement of adjacent bacterial genes under the control of the same operator called?

The arrangement of adjacent bacterial genes that are under the control of the same operator is known as an operon. This organization allows for the coordinated regulation of genes that often work together in a common metabolic pathway. An operon typically consists of one or more structural genes, which code for proteins, alongside regulatory sequences such as the promoter and operator that control the transcription of these genes.

In bacteria, operons enable the efficient use of resources by allowing the simultaneous expression of genes that are functionally related. For example, in the lac operon of E. coli, genes that are responsible for the metabolism of lactose are clustered and regulated together, allowing the bacteria to quickly respond to the availability of lactose.

Other terms such as "cluster" or "gene pair" do not specifically refer to this tightly controlled arrangement and often denote less formal arrangements of genes. A regulatory gene refers to a gene that codes for a protein (like a repressor) involved in the regulation of operons but does not describe the arrangement of the genes themselves. Thus, operon is the most accurate and precise term for describing this arrangement in bacterial genetics.