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Unformatted text preview: BIO 320 - CELL BIOLOGY Spring 2010 A. De Lozanne Lectures 20 22 DNA Replication, Mitosis and the Cell Cycle Reading: Alberts, 5th Ed. Pages. Chapter 17 (pages 1053-1106) - the following sections: An Overview of the Cell Cycle The eukaryotic cell cycle is divided into four phases. Cell-cycle control is similar in all eukaryotes. Cell-cycle control can be dissected genetically by analysis of yeast mutants. Cell-cycle control can be analyzed biochemically in animal embryos. Cell-cycle control can be studied in cultures mammalian cells. Cell-cycle progression can be studied in various ways. The cell-cycle control system The cell-cycle control system triggers the major events of the cell cycle. The cell-cycle control system depends on cyclically activated CDKs. Inhibitory phosphorylation and CDK inhibitory proteins can suppress CDK activity. The cell-cycle control system depends on cyclical proteolysis. Cell-cycle control also depends on transcriptional regulation. The cell-cycle control system functions as a network of biochemical switches. S-Phase S-Cdk initiates DNA replication once per cell cycle. Cohesins help hold sister chromatids together. Mitosis M-Cdk drives entry into mitosis. Dephosphorylation activates M-Cdk at the onset of mitosis. Condensin helps configure duplicated chromosomes for separation. The mitotic spindle is a microtubule-based machine. Microtubule-dependent motor proteins govern spindle assembly and function. Two mechanisms collaborate in the assembly of a bipolar mitotic spindle. Centrosome duplication occurs early in the cell cycle. M-Cdk initiates spindle assembly in prophase. The completion of spindle assembly in animal cells requires nuclear envelope breakdown. Microtubule instability increases greatly in mitosis. Mitotic chromosomes promote bipolar spindle assembly. Kinetochores attach sister chromatids to the spindle. 1 BIO 320 - CELL BIOLOGY Spring 2010 A. De Lozanne Bi-orientation is achieved by trial and error. Multiple forces move chromosomes on the spindle. The APC/C triggers sister chromatid separation and the completion of mitosis. Unattached Chromosomes block sister-chromatid separation. Chromosomes segregate in anaphase A and B. Segregated chromosomes are packaged in daughter nuclei at telophase. Cytokinesis Actin and Myosin II in the contractile ring generate the force for cytokinesis. The microtubules of the mitotic spindle determine the plane of animal cell division....
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- Spring '09