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

Mitosis Interphase Prophase Metaphase Anaphase Telophase Replication Alignment Separation

Fig G 2 of Interphase Centrosomes (with centriole pairs) Chromatin (duplicated) Nucleolus Nuclear envelope Plasma membrane Early mitotic spindle Aster Centromere Chromosome, consisting of two sister chromatids Prophase Prometaphase Fragments of nuclear envelope Nonkinetochore microtubules Kinetochore microtubule Metaphase plate Spindle Centrosome at one spindle pole Anaphase Daughter chromosomes Telophase and Cytokinesis Cleavage furrow Nucleolus forming Nuclear envelope forming

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.