1. CELL DIVISION BIOLOGY 106

2. OUTLINE - Types of cell division - Mitosis o Phases of mitosis o Diagram shows how mitosis works - Meiosis o Phases of meiosis o Diagram shows how meiosis works

3. MITOSIS - This type of cell division allows multicellular organism to grow and repair damage tissue. - Mitosis produce two daughter cells that are identical to the parent cell.

4. MITOSIS SUBDIVIDED INTO 5 PHASES Interphase: takes about 90% of the cell cycle -The cell can grow and copy its chromosomes. o 1- Prophase o 2-Prometaphase o 3-Metaphase o 4-Anaphase o 5-Telophase Cytokinasis

5. o 1- Prophase -Chromosome condensed and become shorter -Nucleoli disappear -The centrosomes duplicate and mitotic spindle fibers begin to form. o 2-Prometaphase -The nuclear envelope fragmented. -The chromosomes become shorter and attached to spindle fibers.

6. o 3-Metaphase -The centrosomes are at the opposite poles of the cell. -The chromosomes arranged on the metaphase plate. o 4-Anaphase -Tow sister chromatids are separated. -Chromatids moving toward the opposite poles

7. o 5-Telophase -Tow daughter nuclei are formed -Nuclear envelope arises -Chromosomes become less condensed. -Spindle fibers disappear  Cytokinesis: Cytoplasm begins to divide in order to give tow daughter cells that have the same number of chromosomes and genetically identical to the mother cells.

8. MITOSIS

9. MEIOSIS Enable the organisms to reproduce sexually. Occurs only in the gonad (Ovary & testis) Gives rise to male and female gametes. Involves tow nuclear division producing 4 daughter cells.

10. MEIOSIS Meiosis I (Reduction division) 1- Prophase I 2- metaphase I 3- Anaphase I 4- Telophase I  Cytokinesis Meiosis II (Mitotic division) - See mitotic division

11. MEIOSIS I (REDUCTION DIVISION) 1- Prophase I A)Chromosomes condensed & become shorter. B)Disappearance of nucleolus & nuclear envelope C)Formation of spindle fibers D)Homologues pairs of chrmosomes are united together E)Crossing over occures….

12. 2- metaphase I -Pair of homologues chromosomes arrange at equator (Metaphase plate) -Chromosomes attach to the spindle fibers. 3- Anaphase I - Separation of homologues pairs of chrmosomes. 4- Telophase I -Nucleolus & nuclear membranes reappear. -Spindle fiber disappear.

13.  Cytokinesis : -Occurs by dividing the cell into tow daughter cells. -The producing cells have half chromosomal of mother cells and differ genetically from them

15. MITOSIS VS MEIOSIS