FIGURE 1 Mitotic cyclins limit entry into mitosis. In all experiments, mitotic CDK activity and mitotic cyclin concentrations were determined at various times after addition of sperm nuclei to a Xenopus egg extract treated as indicated in each panel. Microscopic observations determined the occurrence of early mitotic events (blue shading), including chromosome condensation and nuclear envelope disassembly, and of late mitotic events (orange shading), including chromosome decondensation and nuclear envelope reassembly. See text for discussion. See A. W. Murray et al., 1989, Nature 339:275.
[Data from A. Murray and T. Hunt, 1993, The Cell Cycle: An Introduction, W. H. Freeman and Company.]