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Learn about chromosomal DNA molecules, chromosome duplication, sister chromatids, and the phases of mitosis including prophase, metaphase, anaphase, and telophase. Explore the detailed process step-by-step with the help of Figure 12.5-3. Discover the significance of centromeres, chromosome arms, and the separation of sister chromatids. Follow the continuous process from interphase to cytokinesis. Watch an engaging movie illustrating mitosis.
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Cell Cycle and Mitosis pp.149-151
ChromosomalDNA molecules Chromosomes Figure 12.5-3 Centromere 1 Chromosomearm Chromosome duplication(including DNA replication)and condensation 2 Sisterchromatids Separation of sisterchromatids intotwo chromosomes 3
Cell Cycle • 3 major phases • Interphase: time between cell divisions • G phases: growth • S phase: copying of DNA • M phase (mitosis): division of the nucleus • Cytokinesis: division of the cytoplasm
Mitosis (M phase) • 2n “4n” 2 (2n) • Continuous process starts with interphase • Separate the doubled chromosomes • Four phases • prophase metaphase anaphase telophase
Prophase • Can see chromosomes • Chromatids stay connected by centromeres • Nuclear membrane break down • Centrosomes and centrioles appear and early mitotic spindle forms
Metaphase • Two types of fibers (mitotic spindle) • kinetochore fibers: attach to centromere of chromosome • polar fibers: extend centrosome to centrosome, push cell apart • Fibers line up the chromosomes in middle
Anaphase • Chromatids are pulled apart by fibers • Move towards opposite poles of dividing cells
Telophase • Chromosomes in opposite ends • Spindle fibers break down • Nucleus reforms • Cytokinesis