AP BIOLOGY

Detailed explanation-1: -Cyclins. Cyclins are among the most important core cell cycle regulators.

Detailed explanation-2: -Cell cycle progression is regulated in part by the sequential activity of various cyclins. The cyclins are regulatory subunits that bind, activate and provide substrate specificity for their catalytic partner serine-threonine kinases, collectively called cyclin-dependent kinases (Cdks) (reviewed in refs.

Detailed explanation-3: -Cyclins bind to and activate CDKs. The activity and substrate specificity of any given CDK is primarily defined by the particular cyclin to which it is bound. Cyclins are only present during the cell cycle stage that they trigger and are absent in other cell cycle stages.

Detailed explanation-4: -The cell cycle is controlled by proteins known as cyclins and cyclin-dependent kinases.