There are lot's of different systems in biology that act in this manner. for example gene A produce transcription factor that repress gene B production and vice versa. 

you can refer to this papers for review:

Bistability, Bifurcations, and Waddington’s Epigenetic Landscape. James E. Ferrell

or

Quantifying the Waddington landscape and biological paths for development and differentiation. Jin Wanga et al.

They have derived governing differential equations and they have done some dynamical system analysis like bifurcation analysis.

http://www.cell.com/current-biology/fulltext/S0960-9822(12)00332-6

http://www.pnas.org/content/108/20/8257.long

Hi,

Please follow PIF4 and IBH1 regulation in this paper:

Helix–loop–helix/basic helix–loop–helix transcription factor network represses cell elongation in Arabidopsis through an apparent incoherent feed-forward loop.

Hope it helps.

For example, some of the loops in mammalian circadian clocks:

http://d2qiws50qrj9uc.cloudfront.net/content/develop/141/16/3105/F1.large.jpg