Assays for CDK activity and DNA replication in the cell cycle.

This unit describes two assays for different stages of the cell cycle in tissue culture cells. One is a biochemical measurement that assays the protein kinase activity of different cyclin-dependent kinase complexes that are present in late G1 phase, S phase, G2 phase, or mitosis. The other assay uses immunofluorescence to detect DNA replication by the incorporation of nucleotide analogs into DNA. These assays are useful in analyzing the stage and degree of synchrony of the cell cycle and changes in the basic cell cycle machinery.