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: -The central components of the cell-cycle control system are cyclin-dependent protein kinases (Cdks), whose activity depends on association with regulatory subunits called cyclins. Oscillations in the activities of various cyclin-Cdk complexes leads to the initiation of various cell-cycle events.

Detailed explanation-3: -Cyclin/CDK complexes are known to regulate both mitotic and meiotic cell cycles. While some mechanisms are common to both types of cell divisions, meiosis has unique characteristics and requirements. During meiosis, DNA replication is followed by two successive rounds of cell division.

Detailed explanation-4: -Cyclin A is a pivotal regulatory protein which, in mammalian cells, is involved in the S phase of the cell cycle. Transcription of the human cyclin A gene is cell cycle regulated.

Detailed explanation-5: -The four major mechanisms of CDK regulation are cyclin binding, CAK phosphorylation, regulatory inhibitory phosphorylation, and binding of CDK inhibitory subunits (CKIs).