Lesson #5CELL DIVISION: MITOSIS AND CYTOKINESIS

MITOSIS CELL DIVISION

MITOTIC PHASE Division of a cell into 2 identical cells, with the same amount of DNA.

1. Mitosis: division of the nucleus

2. Cytokinesis: division of the cytoplasm

2n

2n

2n

Parent cell

Daughter cells

Identical nuclei

DNA Replication◦ All DNA molecules need to be doubled o replicated in order for the cell

to be able to make 2 nuclei out of one. Each nucleus must receive the same DNA molecules.

◦ Takes place during Interphase (Phase S)

MITOSIS: Nuclear division Four main phases

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

MITOSIS1. PROPHASE◦ Chromatin condenses into structures called chromosomes ◦ Spindle forms and centrioles migrate to the poles ◦ Nuclear membrane disassembles.◦ Nucleolus disassembles.

MITOSIS2. METAPHASE◦ Chromosomes align in the metaphase plate at the equator of the

cell.◦ Centrosomes are at opposite poles.◦ Mitotic spindle fibers connect with the kinetocore

MITOSIS3. ANAPHASE◦ Chromosomes align in the center. ◦ Centrosomes are at opposite poles◦ Mitotic spindle fibers connect with the kinetocore

MITOSIS4. TELOPHASE◦ Chromatids reach the opposite poles of the cell. ◦ There is a copy of each DNA molecule in each side. ◦ Nuclear envelope and nucleolus begin to reappear.◦ Chromosomes uncoil and become less condensed.◦ Two new nuclei are formed. The is still just 1 cell, but with 2

nuclei.

CytokinesisCytoplasm divides, cell membrane surrounds each or the two daughter cells, leaving a nucleus in each side and hence allows for the completion of cell division. In animal cells: ◦ A contractile ring forms around the equator of the cell. ◦ The contractile ring shrinks at the equator of the cell, pinching the

plasma membrane inward, forming a cleavage furrow. ◦ Eventually, there are two separate cells each with its own nucleus

and surrounded by its own plasma membrane.Source: Scitable. By Nature Education

http://www.argosymedical.com/Cellular/samples/animations/Mitosis/index.html

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