Theory 30/Cellular/Cell fate
Fate Is Concentration Against Sites
The claim
A cell fate decision is set by the ratio of transcription factor concentration to the number of functional binding sites, so the same concentration gives different decisions in different cells.
01Mechanism
Occupancy depends on both; below a ratio the response is graded, above it is switch-like.
02Prediction
Decision sharpness should track the ratio.
03Refutation
Decision tracking concentration would remove site number.