Download 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
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Prophase
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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
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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