AP BIOLOGY

Detailed explanation-1: -During the mitotic cell cycle, cyclins from the D-type family (D1, D2 and D3) regulate progression of cells through the G1 phase. D-type cyclins bind and activate Cdk4 and Cdk6.

Detailed explanation-2: -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-3: -Abstract. DNA replication and mitosis are dependent on the activity of cyclin-dependent protein kinase (CDK) enzymes, which are heterodimers of a catalytic subunit with a cyclin subunit. Cyclin binding to specific individual proteins is thought to provide potential substrates to Cdk.

Detailed explanation-4: -When a cyclin attaches to a Cdk, it has two important effects: it activates the Cdk as a kinase, but it also directs the Cdk to a specific set of target proteins, ones appropriate to the cell cycle period controlled by the cyclin.