Some Feed-Forward Motifs Are Capable of Generating a Brief Pulse

Multiple Choice

Some feed-forward motifs are capable of generating a brief pulse of gene activation in response to a sustained input signal: in such motifs, the signal activates an activator (A) and a repressor (R) , both of which control the expression of the same gene. The quantitative output of the gene depends in part on the relative affinities of A and R for binding to the cis-regulatory sequences of the target gene. Under which of the following conditions is a brief pulse of gene activation observed in response to a sustained input signal? KA and KR are the association constants for A and R, respectively.

A) KA = KR
B) KA << KR
C) KA >> KR
D) KAKR > 1