PATHOLOGY

Detailed explanation-1: -Cyclins. Cyclins are among the most important core cell cycle regulators. Cyclins are a group of related proteins, and there are four basic types found in humans and most other eukaryotes: G 1start subscript, 1, end subscript cyclins, G 1start subscript, 1, end subscript/S cyclins, S cyclins, and M cyclins.

Detailed explanation-2: -Cell cycle-dependent gene transcription is tightly controlled by the retinoblastoma (RB):E2F and DREAM complexes, which repress all cell cycle genes during quiescence. Cyclin-dependent kinase (CDK) phosphorylation of RB and DREAM allows for the expression of two gene sets.

Detailed explanation-3: -The central machines that drive cell cycle progression are the cyclin-dependent kinases (CDKs). These are serine/threonine protein kinases that phosphorylate key substrates to promote DNA synthesis and mitotic progression.