A molecule may be described as cis-acting when it affects other entities only if they are physically adjacent. It may be considered 'the opposite' of a 'trans-acting' molecule.

It is common to describe transcription factors as either cis- or trans-acting. A cis-acting transcription promoter facilitates the transcription of adjacent polypeptide-encoding sequences whereas trans-acting promoters affect the transcription of regions of DNA not in close physical proximity.

Chemistry | Genetics