MICROANATOMY

Detailed explanation-1: -At the heart of the cell-cycle control system is a family of protein kinases known as cyclin-dependent kinases (Cdks). The activity of these kinases rises and falls as the cell progresses through the cycle.

Detailed explanation-2: -Cyclins are a family of proteins that have no enzymatic activity of their own but activate CDKs by binding to them. CDKs must also be in a particular phosphorylation state-with some sites phosphorylated and others dephosphorylated-in order for activation to occur.

Detailed explanation-3: -Cyclin is a family of proteins that controls the progression of a cell through the cell cycle by activating cyclin-dependent kinase (CDK) enzymes or group of enzymes required for synthesis of cell cycle.

Detailed explanation-4: -The most important regulatory control that restricts cyclins to the appropriate cell cycle stage is ubiquitin-mediated protein degradation. Cyclins are degraded through the action of two different ubiquitin-proteins: a) SCF (Skp1, Cullin & f-box proteins)