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Cell Cycle and Mitosis. pp.149-151. Chromosomal DNA molecules. Chromosomes. Figure 12.5-3. Centromere. 1. Chromosome arm. Chromosome duplication (including DNA replication) and condensation. 2. Sister chromatids. Separation of sister chromatids into two chromosomes. 3. Cell Cycle.
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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