Cyclin plays a vital role in the cell division of the cell cycle. At the end of G2 pause, cyclin combines with CDK. Once this happens, MPF is activated and now can enter into the mitotic phase of cell division. As cyclin accumulates MPF is able to pass the next checkpoint. As cyclin increase, MPF increases in activity. Once the MPF decomposes, cyclin turns in CDK/ This CDK is used as recycled material in the next cell division where the new cyclin joins with the recycled CDK to restated the process over again and finish out cell replication. Cyclin helps activate MPF so the cell can enter mitosis.