For full activation of a cyclin-CDK complex, an enzyme called CDK-activating kinase must phosphorylate an amino acid near the CDK active site.
CDK-activating kinase (CAK) actuates the cyclin-CDK complex by phosphorylation of an amino acid i.e. threonine residue 160 near the CDK active site.
CAK is a member of the CDK family and serves as a positive regulator of CDK1, CDK2, CDK4, as well as CDK6.
CDK activation needs two steps. Primarily, the cyclin should attach to the CDK and secondly, CAK should phosphorylate the cyclin-CDK complex on the threonine residue 160, that is situated in the CDK activation section.
Relative dating is used to arrange geological events, and the rocks they leave behind, in a sequence. The method of reading the order is called stratigraphy (layers of rock are called strata). Relative dating does not provide actual numerical dates for the rocks.
