Transcript Mitosis
Warm-up 12/2: • Why do cells replicate their DNA? • When do cells replicate their DNA? • What is the primary purpose of DNA? Chromosomes pp. 151-153 Cell Cycle and Mitosis pp.154- 158 Chromosomes: coiled and compact DNA in nucleus • DNA wrapped tightly around proteins called histones • chromatids: two halves of a dividing chromosome • Chromatids joined by a centromere Chromosome number: each organism has a specific number of chromosomes • Sex chromosomes: determine sex of the organism (X or Y) female: XX male: XY • Autosomes: all other chromosomes • All organisms have two copies that are homologous Cell Cycle and Mitosis 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 Need to separate the doubled chromosomes Four phases prophase metaphase anaphase telophase • PMAT • • • • Prophase • • • • • Can see chromosomes Chromatids stay connected by centromeres Nucleolus and nuclear membrane break down Centrosomes and centrioles appear Early mitotic spindle forms Metaphase • Two types of fibers (mitotic spindle) kinetechore fibers: attach to centromere of chromosome polar fibers: extend centrosome to centrosome, push cell apart • Fibers line up the chromosomes in middle Anaphase • Chromatids of each chromosomes are pulled apart by fibers • Move towards opposite poles of dividing cells Telophase • • • • • Chromosomes in opposite ends Spindle fibers break down Nuclear envelope reforms Nucleolus in each cell Cytokinesis MOVIE Homework • PQRST 154-159 Due Wednesday • Cover Page Due Tomorrow • Notebook Check Tomorrow – Order online