Figure 1.

The types of regulatory genetic variation so far found. (1) cis-regulatory, non-coding; (2) cis-regulatory, coding; (3) trans-regulatory, coding or non-coding (although no instance of polymorphism in the expression of a transcription factor has yet been reported); (4) cis-regulatory, non-coding, very long distance (position effects). The transcription factor is shown in blue, signal sequence shown in red.