. "Cyclin A is synthesized and associates with Cdc2 in G1. Cyclin dependent kinases are themselves catalytically inactive due to the fact that their active sites are blocked by a portion of the CDK molecule itself. Binding to their corresponding cyclin partner results in a conformational change that partially exposes the active site."^^ . . . . . . . "Formation of Cyclin A:Cdc2 complexes"^^ . . . .