| Noun | 1. | regulatory gene - a gene that produces a repressor substance that inhibits an operator gene cistron, gene, factor - (genetics) a segment of DNA that is involved in producing a polypeptide chain; it can include regions preceding and following the coding DNA as well as introns between the exons; it is considered a unit of heredity; "genes were formerly called factors" operon - a segment of DNA containing adjacent genes including structural genes and an operator gene and a regulatory gene |