constitutive

In biology, constitutive refers to any molecule that is constantly produced or to any gene that is constantly expressed (without need for regulatory stimulation by regulatory proteins or transcription factors).

Also referred to as 'wild-type', such genes are to be contrasted with inducible genes, which are subject to up-and down-regulation. Molecules such as proteins and RNAs that are not constitutive have cellular levels that are regulated by protein degradation or RNA decay.