The transition from G2 to M phase of the cell cycle is controlled by :

Ans. is' D i.e. Cyclin BRef Robbins Illustrated 6th/e 284Cyclins control the passage of cells through specific phases of the cell cycleThe entry and progression of cells through the cell cycle are controlled by changes in levels and activities of cyclinsSo the levels of several of the cyclins peak during specific phases of the cell cycle, they are rapidly degraded as the cell enters the next phase of the cell cycleCyclins perform their function by forming a complex with a group of constitute expressed proteins called cyclin-dependent kinases (CDKs).Different combination of cyclins and CDKs are associated with each of the important transitions in the cell cycle.As the cell moves into any phase the cyclin specific for that phase is synthesized and then it binds to its constitutive CDK, creating the cyclin/CDK complex, whose activity is necessary for cells to enter the next phase.This complex when activated participates in the reactions and after the reactions are over these cyclins are degraded.Examples of cyclin/CDK complexes controlling the cell cycle cyclins B/CDK1Regulates the transition from G2 to M phaseCyclin D/CDK4 Cyclin D/CDK6 Cyclin E/CDK2regulates the transition from G1-SCyclin A/CDK2 and cyclin B/CDK1Active in S phase