2. 2.5.1 Cell Cycle

3. 2.5.2 Uncontrolled cell division: tumour cells The cell division cycle is regulated in a number of ways. Certain agents can damage these regulatory elements. When this happen, uncontrolled cell division can occur resulting in the formation of tumours.

4. 2.5.2 Uncontrolled cell division: tumours cells

5. S OF INTERPHASEG2 OF INTERPHASEMITOTIC PHASE 2.5.3 Interphase

6. 2.5.4 The phases of Mitosis: Prophase MTOC (pair centrioles) 1.Chromosomes supercoil and become visible 2.The spindle of microtubules forms from the MTOC (microtubule organizing centre) 1.In animal cell, the centrioles divide and move to opposite ends (poles) of the nucleus. 2.In plant cells, there are no centrioles and the spindle microtubules forms independently. 3.Each chromosome consists of two chromatids held together by the centromere. 4.Nuclear envelop breaks down.

7. 1.Spindle microtubules attaches to the chromosomes by means of the centromere. 2.Chromosomes are moved to the equator of the cell, 2.5.4 The phases of Mitosis: Metaphase

8. The pair of sister chromatids separate and the spindle microtubules pull them towards opposite poles of the cell. 2.5.4 The phases of Mitosis: Anaphase

9. 1.The chromatids have now reached the poles and can be regarded as distinct chromosomes. 2.The nuclear envelop forms around each group of chromosomes. 3.Chromosomes uncoil 4.The cytoplasm divide by a process called Cytokinesis. 2.5.4 The phases of Mitosis: Telophase

10. Cytokinesis: Cytoplasm division

11. 2.5.5 Explain how mitosis produce two genetically identical nuclei

12. Reproduction. An ameba, a single-celled eukaryote, is dividing into two cells. Each new cell will be an individual organism Growth & Development. A sand dollar embryo shortly after the fertilized egg divided forming two cells. Tissue renewal. This dividing bone marrow cells (arrow) will give rise to new blood cells. 2.5.6 Why do cells divide? 1.Asexual Reproduction 2.Growth & Embryonic Development 3.Tissue Renewal