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Transcript
Outline – Cell Reproduction How Cells Divide Why do cells divide? Cell reproduction in prokaryotes Cell cycle Chromosome structure Cell Division: Mitosis & Cytokinesis Cancer & Cell Division Fig. 11.2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Binary Fission in Prokaryotes 1. Replication of DNA Why do cells reproduce? Prokaryote Cell 1. Single celled organisms – reproduction of species 2. Cell Growth 2. Multicellular organisms 3. FtsZ Protein ring forms 1. Growth – increase number of cells 4. Septum Forms 2. Maintenance of existing cells 3. Repair of damaged cells 5. Daughter cells form Daughter Cells 3 3 1 Fig. 11.5 Cell Division in Prokaryotes Chromosome Structure 1. Genetic information = single, circular DNA 2. Prokaryotic cell division = binary fission 3. DNA replication is first. 4. Protein ring forms. 5. Septum (cross wall) forms. 6. One genome goes to each daughter cell Fig. 06.05 Karyotype Genome Size Varies and Homologous Chromosomes 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 11.6 Chromosome Structure 4. Scaffold protein Chromosome Structure and Replication 5. Chromatin loop 30 nm DNA Histone 3. Solenoid 2. Nucleosome (200 nucleotides) 6. Chromatin loops 1. DNA 7. Chromosome 1.4 X106 nucleotides per chromosome Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cell Cycle Cell Cycle M Mitosis (M) Metaphase Prophase Cytokinesis (C) Anaphase Telophase C C G2 G2 Interphase = G1 S G2 S Interphase (G1, S, G2 phases) Mitosis (M) G0 G1 S Cytokinesis (C) Go G1 3 Cell Cycle Mitosis in Eukaryotes • Interphase – G1 – primary growth phase – S – DNA synthesis – Genome replication – G2 – Preparation for mitosis – Chromosomes condense – Organelles replicate Stages of Mitosis Prophase Metaphase • Reproductive Phase Anaphase – M – Mitosis - Separation of Chromosomes – C – Cytokinesis – Cytoplasm divides • G0 – Resting or expression of cell fate. Fig. 11.12b(TE Art) Mitosis – Separation of chromosomes “Division” of nucleus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Interphase (at G2) Telophase Cytokinesis – Separation of cytoplasm Fig. 11.12f(TE Art) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Kinetochore MITOSIS Prophase Nucleus Centrioles Chromosomes condensing Nuclear membrane Chromatin (replicated) Aster 1. DNA has replicated 2. Centrioles replicate Mitotic spindle beginning to form Centromere and kinetochore •Nuclear membrane disintegrates •Nucleolus disappears •Chromosomes condense •Mitotic spindle begins to form and is complete at end of prophase •Kinetochores form at centromeres and attach to spindle 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 11.11(TE Art) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Metaphase Chromosome MITOSIS Metaphase Centrioles Chromosome Aster Microtubules Aster Metaphase plate Spindle fibers Cohesin proteins Chromatid Centromere region of chromosome Kinetochore Microtubules Polar Microtubules Aster Microtubules Kinetochore Kinetochore microtubules Sister Chromatids 18 Fig. 11.12o(TE Art) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. MITOSIS Anaphase Fig. 11.12p(TE Art) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. MITOSIS Telophase Chromosomes Polar Microtubules of Spindle Apparatus Polar microtubules elongate Kinetochore microtubules get shorter •Polar microtubules continue to elongate •Chromosomes reach poles of cell •Kinetochores disappear •Nuclear membrane re-forms •Nucleolus reappears •Chromosomes decondense 5 Fig. 11.12n(TE Art) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mitosis in Plant Cells Cytokinesis Cell plate in plant cells Cell plate Animal Cells form a Cleavage furrow Plant cells: cell plate forms Animal cells: cleavage furrow forms Interfering with Cell Division Cancer therapies: Controlling the Cell Cycle Radiation & Chemotherapy Periwinkle - Vinblastin Pacific Yew - Taxol Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 11.16(TE Art) G2 / M checkpoint Control of Cell Cycle Spindle checkpoint M Inhibitory phosphate C G2 2. Attachment of activating phosphates by CdK Control of the Cell Cycle S 1. Attachment of cyclins to activate cyclin dependent kinase (CdK) G1 3. Removal of inhibitory phosphates by phosphatase Activating phosphate G1 / S checkpoint (START or Restriction Point) Fig. 10.20 Fig. 10.22 Signal transduction pathway 7 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Key Proteins in Human Cancers PROTO-ONCOGENES Growth factor receptor: more per cell in many breast cancers. Ras Signal protein transduction pathway Src kinase Cytoplasm Rb protein Tumors Ras protein: activated by mutations in 20–30% of all cancers. Src kinase: Tumor activated by mutations in 2–5% of all cancers. Lymph vessels Blood vessel TUMOR-SUPPRESSOR GENES Nucleus p53 protein Cyclins Cyclin-Dependent Kinases Phosphatases Rb protein: mutated in 40% of all cancers. p53 protein: Continue Past Cell cycle checkpoints mutated in 50% of all cancers. Single cancer cell Invade Neighboring Tissue Metastasize END Mitosis END Mitosis 8