Also known as a transacting element and a transcriptional regulatory element, it is a gene whose protein controls the activity and expression of one or more structural genes or metabolic pathways. In the Jacob-Monod operon model, these hypothetical genes acted only as repressors, but in later models they were assigned both repressor and activator roles. Thus, they became genes for turning and off the transcription of structural genes and therefore for controlling the timing of development. It is thought that regulator genes account for differences in morphological development among primates, and thus indirectly have an influence on behavior.
See DNA (deoxyribonucleic acid), Gene, Jacob-Monod operon model, Phyletic gradualism and punctuated equilibrium, Structural genes