Math 5110/6830
Homework 9.2
Consider the model of ”START” regulation from class.
1. In Matlab plot both nullclines for α = 2.5 and 3.8. Set other parameters
at κs = 1, κi = .1, κa = .001 λ = 37 and µ = 4. In each case hand-draw
direction field and representative trajectories in the phase plane.
What happens, according to your phase planes, if the level of the transcription factor goes up while the cell is still small?
What happens to the amount of cyclin in a small cell if initially the amount
of cyclin is high and the amount of the active transcription factor s is low?
What is the explnation for this? What if the cyclin was degraded slower? What
parameter would you need to change in the model?
2.(Extra credit) Sketch a bifurcation diagram n vs α
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