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Transcript
Chapter 12: The Cell Cycle: Cell Growth, Cell Division AP Biology Why do cells divide? For reproduction asexual reproduction one-celled organisms For growth from fertilized egg to multi-celled organism For repair & renewal AP Biology replace cells that die from normal wear & tear or from injury amoeba Sexual Reproduction Getting from there to here… Going from egg to baby…. the original fertilized egg has to divide… and divide… and divide… and divide… AP Biology Asexual Reproduction on a Large Scale AP Biology Chromosome numbers in somatic and gamete cells AP Biology Both Binary Fission and Mitosis Produce Genetically Identical Cells Four events must occur for cell division: • Reproductive signal—to initiate cell division • Replication of DNA • Segregation—distribution of the DNA into the two new cells • Cytokinesis—division of the cytoplasm and separation of the two new cells AP Biology Binary Fission In prokaryotes, cell division results in reproduction of the entire organism. Two important regions in reproduction: •ori - where replication starts •ter - where replication ends AP Biology In Eukaryotes: Cell division results in genetically identical daughter cells What is passed on to daughter cells? exact copy of genetic material = DNA mitosis organelles, cytoplasm, cell membrane, enzymes cytokinesis chromosomes (stained orange) in kangaroo rat epithelial cell AP Biology notice cytoskeleton fibers Copying DNA & packaging it… After DNA duplication, chromatin condenses coiling & folding to make a smaller package mitotic chromosome DNA chromatin AP Biology 0.5 µm Chromosomes Chromosome arm DNA molecules Chromosome duplication (including DNA synthesis) Centromere Sister chromatids Separation of sister chromatids Centromere AP Biology Sister chromatids Interphase 90% of cell life cycle cell doing its “everyday job” produce RNA, synthesize proteins/enzymes AP Biology prepares for duplication if triggered Overview of mitosis interphase prophase I.P.M.A.T. (pro-metaphase) cytokinesis AP Biology metaphase anaphase telophase 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 cell grows & matures to never divide again liver cells G1G0 brain / nerve cells muscle cells Interphase Divided into 3 phases: G1 = 1st Gap (Growth) cell doing its “everyday job” cell grows S = DNA Synthesis copies chromosomes G2 = 2nd Gap (Growth) prepares for division cell grows (more) produces organelles, proteins, membranes AP Biology G0 green = key features Interphase Nucleus well-defined DNA loosely packed in long chromatin fibers Prepares for mitosis replicates chromosome DNA & proteins AP Biology produces proteins & organelles S phase: Copying / Replicating DNA Synthesis phase of Interphase dividing cell replicates DNA must separate DNA copies correctly to 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 in mammalian genome ~30 errors per cell cycle mutations (to somatic (body) cells) AP Biology ACTGGTCAGGCAATGTC Organizing DNA DNA DNA is organized in chromosomes histones double helix DNA molecule wrapped around histone proteins like thread on spools DNA-protein complex = chromatin chromatin organized into long thin fiber condensed further during mitosis double stranded chromosome AP Biology duplicated mitotic chromosome doublestranded mitotic human chromosomes AP Biology Mitosis Dividing cell’s DNA between 2 daughter nuclei 4 phases prophase metaphase anaphase telophase AP Biology Chromosome movement Kinetochores use motor proteins that “walk” chromosome along attached microtubule AP Biology microtubule shortens by dismantling at kinetochore (chromosome) end green = key features Telophase Chromosomes arrive at opposite poles daughter nuclei 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 Plant Cell Division Real Time Video Animal Cell Division Video AP Biology Cytokinesis in Animals 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 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 Coordination of cell division A multicellular organism needs to coordinate cell division across different tissues & organs AP Biology GHOSTS AP Biology AP Biology Mitosis in animal cells AP Biology Mitosis in plant cell AP Biology All Sexual Life Cycles Involve Fertilization and Meiosis AP Biology Haplontic life cycle in protists, fungi, and some algae— zygote is the only diploid stage AP Biology Diplontic life cycle—animals and some plants; gametes are the only haploid stage AP Biology green = key features 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 Nucleolus disappears Nuclear membrane breaks down AP Biology green = key features Transition to Metaphase Prometaphase spindle fibers attach to centromeres creating kinetochores microtubules attach at kinetochores connect centromeres to centrioles AP Biology chromosomes begin moving green = key features 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 Separation of chromatids In anaphase, proteins holding together sister chromatids are inactivated separate to become individual chromosomes 1 chromosome 2 chromatids AP Biology double-stranded 2 chromosomes single-stranded green = key features Anaphase Sister chromatids separate at kinetochores move to opposite poles pulled at centromeres pulled by motor proteins “walking”along microtubules increased production of ATP by mitochondria Poles move farther apart AP Biology polar microtubules lengthen