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Transcript
Biology is the only subject in which multiplication is the same thing as division… AP Biology 2006-2007 The Cell Cycle: Cell Growth, Cell Division AP Biology 2006-2007 Where it all began… You started as a cell smaller than a period at the end of a sentence… AP Biology And now look at you… AP Biology How did you get from there to here? Getting from there to here… Cell division reproduction of cells continuity of life reproduction unicellular organisms growth repair & renew Cell cycle AP Biology life of a cell from origin to division into 2 new daughter cells amoeba Getting the right stuff What is passed on to daughter cells? exact copy of genetic material = DNA mitosis division of organelles & cytoplasm cytokinesis chromosomes (stained orange) in kangaroo rat epithelial cell AP Biology notice cytoskeleton fibers Copying DNA Dividing cell duplicates DNA separates each copy to opposite ends of cell splits into 2 daughter cells human cell duplicates ~3 meters DNA each daughter cell gets complete identical copy error rate = ~1 per 100 million bases 3 billion base pairs mammalian genome ~30 errors per cell cycle mutations AP Biology A bit about DNA DNA DNA is organized in chromosomes histones double helix DNA molecule associated proteins = histone proteins DNA-protein complex = chromatin chromatin organized into long thin fiber AP Biology duplicated chromosome human chromosomes AP Biology Chromosome structure scaffold protein chromatin loop DNA nucleosome histone rosettes of chromatin loops chromosome AP Biology DNA double helix Copying DNA with care… After DNA duplication, chromatin condenses coiling & folding to make a smaller package from DNA molecule to chromatin to highly condensed mitotic chromosome mitotic chromosome DNA chromatin AP Biology Mitotic Chromosome Duplicated chromosome 2 sister chromatids narrow at centromeres contain identical copies of original DNA AP Biology M Mitosis Cell cycle Cell has a “life cycle” cell is formed from a mitotic division cell grows & matures to divide again G1, S, G2, M epithelial cells, blood cells, stem cells AP Biology G2 Gap 2 S Synthesis cell grows & matures to never divide again liver cells G1G0 brain / nerve cells muscle cells G1 Gap 1 G0 Resting M Mitosis Cell Division cycle Phases of a dividing G2 Gap 2 cell’s life interphase S Synthesis G0 Resting cell grows replicates chromosomes produces new organelles, enzymes, membranes… G1, S, G2 mitotic phase cell separates & divides chromosomes mitosis cell divides cytoplasm & organelles cytokinesis AP Biology G1 Gap 1 Interphase 90% of cell life cycle cell doing its “everyday job” produce RNA, synthesize proteins/enzymes prepares for duplication if triggered Characteristics AP Biology nucleus well-defined DNA loosely packed in long chromatin fibers Interphase Divided into 3 phases: G1 = 1st Gap cell doing its “everyday job” cell grows S = DNA Synthesis copies chromosomes G2 = 2nd Gap prepares for division cell grows produces organelles, proteins, membranes AP Biology Interphase Nucleus well-defined chromosome duplication complete DNA loosely packed in long chromatin fibers Prepares for mitosis AP Biology produces proteins & organelles Mitosis Dividing cell’s DNA between 2 daughter nuclei “dance of the chromosomes” 4 phases prophase metaphase anaphase telophase AP Biology Prophase Chromatin condenses visible chromosomes chromatids Centrioles move to opposite poles of cell Protein fibers cross cell to form mitotic spindle microtubules coordinates movement of chromosomes actin, myosin Nucleolus disappears Nuclear membrane breaks down AP Biology Transition to Metaphase Prometaphase spindle fibers attach to centromeres creating kinetochores microtubules attach at kinetochores connect centromeres to centrioles AP Biology chromosomes begin moving Metaphase Chromosomes align along middle of cell metaphase plate meta = middle spindle fibers coordinate movement helps to ensure chromosomes separate properly so each new nucleus receives only 1 copy of each chromosome AP Biology AP Biology Anaphase Sister chromatids separate at kinetochores move to opposite poles pulled at centromeres pulled by motor proteins “walking”along microtubules actin, mysoin increased production of ATP by mitochondria Poles move farther apart polar microtubules AP Biology lengthen Separation of chromatids In anaphase, proteins holding together sister chromatids are inactivated separate to become individual chromosomes 1 chromosome AP Biology 2 chromatids 2 chromosomes Chromosome movement Kinetochores use motor proteins that “walk” chromosome along attached microtubule AP Biology microtubule shortens by dismantling at kinetochore (chromosome) end Telophase Chromosomes arrive at opposite poles daughter nuclei form nucleoli form chromosomes disperse no longer visible under light microscope Spindle fibers disperse Cytokinesis begins AP Biology cell division Cytokinesis Animals constriction belt of actin microfilaments around equator of cell cleavage furrow forms splits cell in two like tightening a draw string AP Biology Cytokinesis in Animals (play Cells Alive movies here) AP Biology (play Thinkwell movies here) Mitosis in whitefish blastula AP Biology Mitosis in animal cells AP Biology Cytokinesis in Plants Plants cell plate forms vesicles line up at equator derived from Golgi vesicles fuse to form 2 cell membranes new cell wall laid down between membranes new cell wall fuses AP Biology with existing cell wall Cytokinesis in plant cell AP Biology Mitosis in plant cell AP Biology onion root tip AP Biology Evolution of mitosis Mitosis in chromosome: double-stranded replication of DNA DNA eukaryotes likely evolved from binary fission in bacteria single circular chromosome no membranebound organelles AP Biology Origin of replication elongation of cell ring of proteins cell pinches in two Evolution of mitosis A possible progression of mechanisms intermediate between binary fission & mitosis seen in modern organisms prokaryotes (bacteria) protists dinoflagellates protists diatoms eukaryotes yeast eukaryotes animals AP Biology Dinoflagellates algae “red tide” bioluminescence AP Biology Diatoms microscopic algae marine freshwater AP Biology Any Questions?? AP Biology 2006-2007