Basal refers to the sort of “baseline” or “normal” levels of something – a system’s “default.” It’s what you see under typical, unperturbed, conditions if you don’t do anything to activate or repress it.
We can use it to describe…
…how active enzymes or receptors are in the absence of activating stimuli
…how highly a gene is regularly expressed (relying only on “generic” transcription factors to get made)
