BLG 311: CELL BIOLOGYWEEK 8INTRODUCTION TO THE CELL CYCLE(Chapter 17)Dr. Hossein NoyanFall 20191
Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K. and Walter, P. 2014. Molecular Biology of the Cell.6thedition. W.W. Norton & Company Inc.BLG311 Required Text2
Objectives•Cell cycle phases•Model systems to study cell cycle•Checkpoints for cell cycle•Control of the cell cycle (cyclins, cyclin-dependent kinases) •Mitosis (with emphasis on the role of the cytoskeleton) •Sister chromatid separation•Telophase3
Cell Cycle is a Cycle of Duplication and Division
•Chromosome duplication occurs during S phase (S for DNA synthesis)•Chromosome segregation and cell division occur in M phase (M for mitosis)
The Events of Eukaryotic Cell Division as Seen Undera Microscope
The Control of the Cell CycleThe cell-cycle control system governs cell-cycle progression at three major regulatory transitions:•Start (or the restriction point) in late G1•The G2/M transition•The metaphase-to-anaphase transition
Two Key Components of the Cell-cycle Control System•Cdks are central components of the cell-cycle control system•Cyclins are regulators of CdkWithout cyclin, Cdk is inactive.
Cyclin–cdk Complexes of the Cell-cycle Control System1. G1/S-cyclins activate Cdks in late G1 and thereby help trigger progression through Start, resulting in a commitment to cell-cycle entry. 2.2. S-cyclinsbind Cdks soon after progression through Start and help stimulate chromosome duplication. S-cyclin levels remain elevated until mitosis, and these cyclins also contribute to the control of some early mitotic events.3. M-cyclins activate Cdks that stimulate entry into mitosis at the G2/M transition.
MITOSISI can’t bear living with you anymore. I want the mitosis now!