the cell cycle & mitosis “omnis cellula e cellula.” “every cell from a cell.” —rudolph...
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The Cell Cycle & Mitosis
“Omnis cellula e cellula.”“Every cell from a cell.”
—Rudolph Virchow, Germany, 1855
Fig. 12-2a
100 µm Reproduction: An amoeba,A single celled eukaryote, divides into two cells. Each new cell will be an individual organism.
Fig. 12-2b
200 µm
Growth and Development: A sand dollar embryo just after the fertilized egg divided.
Fig. 12-2c
20 µm Tissue Renewal: Bone marrow cells form new blood cells.
The Cell Cycle
• The life of a cell from the time it first formed from a dividing parent cell until its own division into two cells.
• Consists of interphase, mitosis & cytokinesis.
Interphase
• The cell grows (increases in mass),• Copies cytoplasmic organelles and• Produces proteins• Duplicates chromosomes• 90% of cell cycle is in interphase
MitosisInterphase Prophase Metaphase Anaphase Telophase
Replication Alignment Separation
Fig. 12-6
G2 of Interphase
Centrosomes(with centriolepairs)
Chromatin(duplicated)
Nucleolus Nuclearenvelope
Plasmamembrane
Early mitoticspindle
Aster Centromere
Chromosome, consisting of two sister chromatids
Prophase Prometaphase
Fragmentsof nuclearenvelope
Nonkinetochoremicrotubules
Kinetochore Kinetochoremicrotubule
Metaphase
Metaphaseplate
Spindle Centrosome atone spindle pole
Anaphase
Daughterchromosomes
Telophase and Cytokinesis
Cleavagefurrow
Nucleolusforming
Nuclearenvelopeforming
Replication
• DNA replicates during interphase.
The Mitotic Spindle
• Spindle fibers made of microtubules and proteins that controls chromosome movement during mitosis.
• Assembled at centrosome in animal cells (MTOC)
Alignment (Prophase & Metaphase)
• Microtubules extend from centrosomes and some attach to kinetochores on the chromatids
• Microtubles move the chromatids until their centromeres lie on the metaphase plate.
Separation—Anaphase & Telophase
• Kinetochore microtubules shorten and pull the chromatids apart
• The chromosomes are pulled to opposite poles of the cell
In animal cells, cytokinesis occurs by forming a cleavage furrow which deepens until the parent cell is pinched in two.
In plant cells, a cell plate forms in the middle of the cell.
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