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Cell Cycle and Mitosis. 9.1 Cell Cycle. What is the cell cycle?. Repeating series of events Five stages Interphase (3 parts) G 1 S G 2 M phase (2 parts) Mitosis Cytokinesis. What happens in Interphase?. G 1 Normal growth Recovery from last mitotic division S
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Cell Cycle and Mitosis 9.1 Cell Cycle
What is the cell cycle? • Repeating series of events • Five stages • Interphase (3 parts) • G1 • S • G2 • M phase (2 parts) • Mitosis • Cytokinesis
What happens in Interphase? • G1 • Normal growth • Recovery from last mitotic division • S • Replication of chromatids • G2 • Synthesis of proteins for mitosis
Cell Cycle and Mitosis 9.2 M phase: Mitosis and cytokinesis
What happens during the M phase? • Mitosis • Prokaryotes undergo binary fission instead • Cytokinesis
What is a chromosome? • Length of DNA with genes and noncoding regions • Highly condensed version of chromatin • Heterochromatin vs. euchromatin
What is mitosis? • Division of nuclear material • Duplicated chromosomes are split • This creates unduplicated chromosomes • Chromosome terminology • Sister chromatids • Kinetechore • Centromere • Diploid (2n) vs. haploid (1n)
What are the stages of mitosis? • Prophase • Prometphase • Metaphase • Anaphase • Telophase
What happens in prophase? • Nuclear envelope disappears • Centrioles move apart • Nucleous disappears • Chromatin condenses to form chromosomes • Recall that these are duplicated
What happens during prometaphase? • Kinetechores appear • Spindles attach • Polar spindle fibers extend and overlap
What happens during metaphase? • Duplicated chromosomes align along metaphase plate
What happens during anaphase? • Sister chromatids pulled apart • Chromosomes are now unduplicated
What happens during telophase? • Reverse of prophase • Cleavage furrow develops in animal cells
What is the second part of the M phase? • Cytokinesis • Cytoplasmic division • Animal cells • Contractile ring • Plant cells • Cell plate
Cell Cycle and Mitosis 9.3 Cell cycle control and cancer
Why do cells undergo mitosis? • Repair and replacement • Apoptosis of somatic cells • blebbing • Stem cells • Serve as reservoir for replacing old cells
What controls the cell cycle? • Checkpoints • G1 • Apoptosis if DNA is damaged • G2 • M
What is cancer? • Uncontrolled cell growth • Characteristics • Neoplasms (tumors) • Benign vs. malignant • Angiogenesis • Metastasis • Abnormal nuclei • Undifferentiated (anaplasia) • Lack contact inhibition • No apoptosis
How does cancer occur? • Mutations of cell repair genes • Activation of telomerase • Mutations of either/both • Proto-oncogenes • Become oncogenes • Tumor suppressor cells
What are proto-oncogenes? • “gas pedal” of cell division • Mutated oncogene • Examples • ras genes • rasN (leukemia) • BRCA1
What are tumor suppressor genes? • Brake pedal of cell division • If mutated loss of cell cycle control • Examples • p53 gene • RB gene