AP BIOLOGY

Detailed explanation-1: -The cell cycle is regulated by many cyclins and cyclin-dependent kinases (CDKs) that are a group of serine/threonine kinases. They form complexes with cyclins to stabilize, activate, and phosphorylate CDKs in the specific phases [6, 7].

Detailed explanation-2: -Cyclins drive the events of the cell cycle by partnering with a family of enzymes called the cyclin-dependent kinases (Cdks). A lone Cdk is inactive, but the binding of a cyclin activates it, making it a functional enzyme and allowing it to modify target proteins.

Detailed explanation-3: -Summary. Cyclin-dependent kinases (CDKs) are protein kinases characterized by needing a separate subunit-a cyclin-that provides domains essential for enzymatic activity. CDKs play important roles in the control of cell division and modulate transcription in response to several extra-and intracellular cues.

Detailed explanation-4: -The four major mechanisms of CDK regulation are cyclin binding, CAK phosphorylation, regulatory inhibitory phosphorylation, and binding of CDK inhibitory subunits (CKIs).

Detailed explanation-5: -Cyclin dependent kinase 20 (CDK20) and p21Cip1/Waf1 are widely recognized as key regulators of cell cycle checkpoints controlling cell proliferation/growth and involving in developing multiple cancers.