THE CELL
CELL COMMUNICATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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PDGF
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MPF
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protein kinase
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cyclin
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Detailed explanation-1: -The correct answer is: a. cyclin: Cyclins are expressed during a specific cell cycle phase.
Detailed explanation-2: -Which of the following is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active? cyclins.
Detailed explanation-3: -The activities of cyclin-dependent kinases (Cdks) control all aspects of cell division, including entry into the cell cycle from quiescence, the G1/S phase transition, DNA replication in S phase, nuclear breakdown, chromosome condensation and segregation, and cytokinesis (1).
Detailed explanation-4: -Formation of the cyclin/CDK complexes results in phosphorylation and activation of the CDKs. Activated cyclin/CDK complexes phosphorylate specific protein substrates that enable cell cycle progression.
Detailed explanation-5: -Cdk/cyclin complexes regulate Rb/E2F-and FoxM1-mediated transcription. During the G1 phase of the cell cycle, Cdk4/cyclin D (cycD) and Cdk2/cyclin E (cycE) complexes sequentially phosphorylate (P) Rb, leading to the activation of E2F proteins and the expression of E2F-responsive genes.