Skip to main content
. 2014 Feb 11;12(2):e1001788. doi: 10.1371/journal.pbio.1001788

Figure 1. The embryonic cell cycle oscillator consists of interlinked positive-and-negative feedback loops.

Figure 1

Cyclin B–Cdk1 inhibits its inhibitory kinases Wee1 and Myt1, forming a double negative feedback loop, which in many respects is equivalent to a positive feedback loop. Cyclin B–Cdk1 activates its activating phosphatase Cdc25, forming a positive feedback loop. Active cyclin B–Cdk1 also activates the E3 ubiquitin ligase APC/CCdc20, which targets cyclin B for degradation. The Cdk1–APC/CCdc20 circuit is therefore a negative feedback loop.